Use new CI scheme from X4

.github/actions/setup-cpp/action.yml

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+# Copyright 2026 The Iris Project Contributors
+#
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+name: Setup Toolchain
+description: Checkout, install compiler, and fetch environment info
+
+inputs:
+  os-name:
+    required: true
+  os-version:
+    required: true
+  compiler-toolset:
+    required: true
+  compiler-version:
+    required: true
+  compiler-executable:
+    required: true
+  compiler-toolset-version:
+    required: false
+    type: string
+    default: ''
+  vs-path:
+    required: false
+    type: string
+    default: ''
+  cpp-version-name:
+    required: true
+  build-type-name:
+    required: true
+
+outputs:
+  compiler-full-version:
+    description: Full version string of the compiler
+    value: ${{ steps.env-info.outputs.compiler-full-version }}
+  deps-cache-key:
+    description: Cache key for CMake dependencies
+    value: ${{ steps.env-info.outputs.deps-cache-key }}
+
+runs:
+  using: composite
+  steps:
+    - name: Initialize Ubuntu
+      if: inputs.os-name == 'ubuntu'
+      shell: bash
+      run: |
+        sudo echo "set man-db/auto-update false" | sudo debconf-communicate
+        sudo dpkg-reconfigure man-db
+
+    - name: Setup GCC
+      if: inputs.compiler-toolset == 'gcc'
+      shell: bash
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y g++-${{ inputs.compiler-version }}
+
+    - name: Setup Clang
+      if: inputs.compiler-toolset == 'clang'
+      shell: bash
+      run: |
+        wget https://apt.llvm.org/llvm.sh
+        chmod +x ./llvm.sh
+        sudo ./llvm.sh ${{ inputs.compiler-version }}
+        sudo apt-get install -y libc++-${{ inputs.compiler-version }}-dev libc++abi-${{ inputs.compiler-version }}-dev libunwind-${{ inputs.compiler-version }}-dev
+
+    - uses: TheMrMilchmann/setup-msvc-dev@v3
+      if: inputs.os-name == 'windows'
+      with:
+        arch: x64
+        vs-path: ${{ inputs.vs-path }}
+        toolset: ${{ inputs.compiler-toolset-version }}
+
+    - name: Fetch Environment Info
+      id: env-info
+      shell: bash
+      run: |
+        set -e
+        case "${{ inputs.compiler-toolset }}" in
+          "gcc")
+            COMPILER_FULL_VERSION=$(${{ inputs.compiler-executable }} -dumpfullversion -dumpversion)
+            ;;
+          "clang")
+            COMPILER_FULL_VERSION=$(${{ inputs.compiler-executable }} -dumpversion)
+            ;;
+          "msvc")
+            COMPILER_FULL_VERSION=$(powershell -NoProfile -Command "(Get-Command ${{ inputs.compiler-executable }}).FileVersionInfo.FileVersion")
+            ;;
+        esac
+        echo "COMPILER_FULL_VERSION=$COMPILER_FULL_VERSION"
+        echo "compiler-full-version=$COMPILER_FULL_VERSION" >> "$GITHUB_OUTPUT"
+        echo "deps-cache-key=deps4-${{ inputs.os-name }}-${{ inputs.os-version }}-${{ inputs.compiler-toolset }}-${COMPILER_FULL_VERSION}-${{ inputs.cpp-version-name }}-${{ inputs.build-type-name }}" >> "$GITHUB_OUTPUT"

.github/workflows/GHA-cleanup.yml

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+# https://docs.github.com/en/actions/how-tos/manage-workflow-runs/manage-caches#force-deleting-cache-entries
+
+name: Cleanup GitHub runner caches on closed pull requests
+on:
+  pull_request:
+    types:
+      - closed
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+    permissions:
+      actions: write
+    steps:
+      - name: Cleanup
+        run: |
+          echo "Fetching list of cache keys"
+          cacheKeysForPR=$(gh cache list --ref $BRANCH --limit 100 --json id --jq '.[].id')
+
+          ## Setting this to not fail the workflow while deleting cache keys.
+          set +e
+          echo "Deleting caches..."
+          for cacheKey in $cacheKeysForPR
+          do
+              gh cache delete $cacheKey
+          done
+          echo "Done"
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+          BRANCH: refs/pull/${{ github.event.pull_request.number }}/merge

.github/workflows/build.yml

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+# Copyright 2026 The Iris Project Contributors
+#
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+name: Build
+
+on:
+  workflow_call:
+    inputs:
+      os-name:
+        required: true
+        type: string
+      os-version:
+        required: true
+        type: string
+      build-type-name:
+        required: true
+        type: string
+      cpp-version-name:
+        required: true
+        type: string
+      cpp-version-number:
+        required: true
+        type: string
+      compiler-toolset:
+        required: true
+        type: string
+      compiler-version:
+        required: true
+        type: string
+      compiler-executable:
+        required: true
+        type: string
+      compiler-cxxflags:
+        required: false
+        type: string
+        default: ""
+      compiler-toolset-version:
+        required: false
+        type: string
+        default: ""
+      vs-path:
+        required: false
+        type: string
+        default: ""
+      cmake-config-additional-args:
+        required: false
+        type: string
+        default: ""
+      compiler-builder-additional-args:
+        required: false
+        type: string
+        default: ""
+      components:
+        required: true
+        type: string
+        description: 'JSON array of components to build (e.g. ["iris", "alloy","x4"])'
+
+env:
+  IRIS_CI_BUILD_JOBS: 4
+
+jobs:
+  prepare-deps:
+    name: "Dependencies"
+    runs-on: ${{ inputs.os-name }}-${{ inputs.os-version }}
+
+    steps:
+      - uses: actions/checkout@v5
+        with:
+          submodules: recursive
+
+      - name: Setup Toolchain
+        id: setup
+        uses: ./.github/actions/setup-cpp
+        with:
+          os-name: ${{ inputs.os-name }}
+          os-version: ${{ inputs.os-version }}
+          compiler-toolset: ${{ inputs.compiler-toolset }}
+          compiler-version: ${{ inputs.compiler-version }}
+          compiler-executable: ${{ inputs.compiler-executable }}
+          compiler-toolset-version: ${{ inputs.compiler-toolset-version }}
+          vs-path: ${{ inputs.vs-path }}
+          cpp-version-name: ${{ inputs.cpp-version-name }}
+          build-type-name: ${{ inputs.build-type-name }}
+
+      - name: Cache CMake Dependencies (restore)
+        id: cache-deps
+        uses: actions/cache/restore@v5
+        with:
+          key: ${{ steps.setup.outputs.deps-cache-key }}
+          path: ${{ github.workspace }}/build/_deps
+
+      # Adapt CMP0168; enable caching in CI
+      # https://cmake.org/cmake/help/latest/module/FetchContent.html#variable:FETCHCONTENT_FULLY_DISCONNECTED
+      - name: Setup Cached CMake Dependencies
+        id: deps-info
+        shell: bash
+        run: |
+          if [ "${{ steps.cache-deps.outputs.cache-hit }}" = "true" ]; then
+            echo "IRIS_CI_CMAKE_ARGS=-DFETCHCONTENT_FULLY_DISCONNECTED=ON" >> "$GITHUB_OUTPUT"
+          else
+            echo "IRIS_CI_CMAKE_ARGS=" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Configure
+        env:
+          CLICOLOR_FORCE: 1
+        shell: bash
+        run: |
+          set -xe
+          cmake ${{ steps.deps-info.outputs.IRIS_CI_CMAKE_ARGS }} -B build \
+            ${{ inputs.cmake-config-additional-args }} \
+            -DCMAKE_CXX_COMPILER=${{ inputs.compiler-executable }} \
+            -DCMAKE_CXX_FLAGS="${{ inputs.compiler-cxxflags }}" \
+            -DCMAKE_CXX_STANDARD=${{ inputs.cpp-version-number }} \
+            -DCMAKE_BUILD_TYPE=${{ inputs.build-type-name }} \
+            -DIRIS_CI=ON \
+            -S .
+
+      - name: Build Deps
+        env:
+          CLICOLOR_FORCE: 1
+        run: |
+          cmake --build build --config ${{ inputs.build-type-name }} -j${{ env.IRIS_CI_BUILD_JOBS }} --target Catch2WithMain ${{ inputs.compiler-builder-additional-args }}
+
+      - name: Cache CMake Dependencies (save)
+        # Due to some bogus "Unable to reserve cache with key" error, we *always* save the cache for now.
+        # See this page for the rate limit: https://docs.github.com/en/actions/reference/limits#existing-system-limits
+        # if: steps.cache-deps.outputs.cache-hit != 'true'
+        uses: actions/cache/save@v5
+        with:
+          key: ${{ steps.cache-deps.outputs.cache-primary-key }}
+          path: ${{ github.workspace }}/build/_deps
+
+  build:
+    name: ${{ matrix.component }}
+    needs: prepare-deps
+    runs-on: ${{ inputs.os-name }}-${{ inputs.os-version }}
+
+    strategy:
+      fail-fast: false
+
+      matrix:
+        component: ${{ fromJSON(inputs.components) }}
+
+    steps:
+      - uses: actions/checkout@v5
+        with:
+          submodules: recursive
+
+      - name: Setup Toolchain
+        id: setup
+        uses: ./.github/actions/setup-cpp
+        with:
+          os-name: ${{ inputs.os-name }}
+          os-version: ${{ inputs.os-version }}
+          compiler-toolset: ${{ inputs.compiler-toolset }}
+          compiler-version: ${{ inputs.compiler-version }}
+          compiler-executable: ${{ inputs.compiler-executable }}
+          cpp-version-name: ${{ inputs.cpp-version-name }}
+          build-type-name: ${{ inputs.build-type-name }}
+
+      - name: Cache CMake Dependencies (restore)
+        id: cache-deps
+        uses: actions/cache/restore@v4
+        with:
+          key: ${{ steps.setup.outputs.deps-cache-key }}
+          path: ${{ github.workspace }}/build/_deps
+
+      - name: Configure
+        env:
+          CLICOLOR_FORCE: 1
+        shell: bash
+        run: |
+          set -xe
+          cmake -DFETCHCONTENT_FULLY_DISCONNECTED=ON -B build \
+            -DCMAKE_CXX_COMPILER=${{ inputs.compiler-executable }} \
+            -DCMAKE_CXX_FLAGS="${{ inputs.compiler-cxxflags }}" \
+            -DCMAKE_CXX_STANDARD=${{ inputs.cpp-version-number }} \
+            -DCMAKE_BUILD_TYPE=${{ inputs.build-type-name }} \
+            -DIRIS_CI_COMPONENT=${{ matrix.component }} \
+            -DIRIS_CI=ON \
+            -S .
+
+      - name: Build Tests
+        env:
+          CLICOLOR_FORCE: 1
+        shell: bash
+        run: |
+          echo "CPPWARNINGNOTIFIER_LOG_MARKER"
+          cmake --build build --config ${{ inputs.build-type-name }} -j${{ env.IRIS_CI_BUILD_JOBS }} ${{ inputs.compiler-builder-additional-args }}
+
+      - name: Test
+        env:
+          CLICOLOR_FORCE: 1
+        working-directory: ${{ github.workspace }}/build/test
+        run: ctest --output-on-failure -C ${{ inputs.build-type-name }}