Merge bitcoin/bitcoin#33425: ci: remove Clang build from msan fuzz job

b77137a ci: link against -lstdc++ in native fuzz with msan job (fanquake)

Pull request description:

  Remove the Clang build from msan fuzz by using the apt install LLVM / Clang, and just linking against `-lstdc++`.

ACKs for top commit:
  maflcko:
    lgtm ACK b77137a

Tree-SHA512: dc32b22a93196120a343d91265db3f42f6dc00afc887929986987ea62f2513580c855e98d088f037adb4c2e62358f98e47b914a412ef9c1069037917a36c0b03

Author: fanquake

ci/test/00_setup_env_native_fuzz_with_msan.sh

@@ -7,12 +7,15 @@
 export LC_ALL=C.UTF-8
 
 export CI_IMAGE_NAME_TAG="mirror.gcr.io/ubuntu:24.04"
+export APT_LLVM_V="21"
 LIBCXX_DIR="/cxx_build/"
 export MSAN_FLAGS="-fsanitize=memory -fsanitize-memory-track-origins=2 -fno-omit-frame-pointer -g -O1 -fno-optimize-sibling-calls"
-LIBCXX_FLAGS="-nostdinc++ -nostdlib++ -isystem ${LIBCXX_DIR}include/c++/v1 -L${LIBCXX_DIR}lib -Wl,-rpath,${LIBCXX_DIR}lib -lc++ -lc++abi -lpthread -Wno-unused-command-line-argument"
+# -lstdc++ to resolve link issues due to upstream packaging
+LIBCXX_FLAGS="-nostdinc++ -nostdlib++ -isystem ${LIBCXX_DIR}include/c++/v1 -L${LIBCXX_DIR}lib -Wl,-rpath,${LIBCXX_DIR}lib -lc++ -lc++abi -lpthread -Wno-unused-command-line-argument -lstdc++"
 export MSAN_AND_LIBCXX_FLAGS="${MSAN_FLAGS} ${LIBCXX_FLAGS}"
 
 export CONTAINER_NAME="ci_native_fuzz_msan"
+export PACKAGES="clang-${APT_LLVM_V} llvm-${APT_LLVM_V} llvm-${APT_LLVM_V}-dev libclang-${APT_LLVM_V}-dev libclang-rt-${APT_LLVM_V}-dev"
 export DEP_OPTS="DEBUG=1 NO_QT=1 CC=clang CXX=clang++ CFLAGS='${MSAN_FLAGS}' CXXFLAGS='${MSAN_AND_LIBCXX_FLAGS}'"
 export GOAL="all"
 # Setting CMAKE_{C,CXX}_FLAGS_DEBUG flags to an empty string ensures that the flags set in MSAN_FLAGS remain unaltered.

ci/test/01_base_install.sh

@@ -58,23 +58,6 @@ fi
 if [[ -n "${USE_INSTRUMENTED_LIBCPP}" ]]; then
   ${CI_RETRY_EXE} git clone --depth=1 https://github.com/llvm/llvm-project -b "llvmorg-21.1.1" /llvm-project
 
-  if [ -n "${APT_LLVM_V}" ]; then
-
-    cmake -G Ninja -B /clang_build/ \
-      -DLLVM_ENABLE_PROJECTS="clang" \
-      -DCMAKE_BUILD_TYPE=Release \
-      -DLLVM_TARGETS_TO_BUILD=Native \
-      -DLLVM_ENABLE_RUNTIMES="compiler-rt;libcxx;libcxxabi;libunwind" \
-      -S /llvm-project/llvm
-
-    ninja -C /clang_build/ "$MAKEJOBS"
-    ninja -C /clang_build/ install-runtimes
-
-    update-alternatives --install /usr/bin/clang++ clang++ /clang_build/bin/clang++ 100
-    update-alternatives --install /usr/bin/clang clang /clang_build/bin/clang 100
-    update-alternatives --install /usr/bin/llvm-symbolizer llvm-symbolizer /clang_build/bin/llvm-symbolizer 100
-  fi
-
   cmake -G Ninja -B /cxx_build/ \
     -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind" \
     -DCMAKE_BUILD_TYPE=Release \