Merge bitcoin/bitcoin#33364: ci: always use tag for LLVM checkout

b736052 ci: always use tag for LLVM checkout (fanquake)

Pull request description:

  Rather than trying to match the apt installed clang version, which is prone to intermittent issues. i.e #33345.

ACKs for top commit:
  davidgumberg:
    ACK bitcoin/bitcoin@b736052
  willcl-ark:
    ACK b736052

Tree-SHA512: 8e3fcc8219f573cec65941576c7995f21cae3330bcdbf615f799e8c5facd1146d3239a7284e9af7b013c37170ddf7435d7df6d2966f63fe7b4a8e4937311ff36

Author: fanquake

ci/test/01_base_install.sh

@@ -56,10 +56,9 @@ if [ -n "$PIP_PACKAGES" ]; then
 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
-    ${CI_RETRY_EXE} git clone --depth=1 https://github.com/llvm/llvm-project -b "llvmorg-$( clang --version | sed --silent 's@.*clang version \([0-9.]*\).*@\1@p' )" /llvm-project
-  else
-    ${CI_RETRY_EXE} git clone --depth=1 https://github.com/llvm/llvm-project -b "llvmorg-21.1.0" /llvm-project
 
     cmake -G Ninja -B /clang_build/ \
       -DLLVM_ENABLE_PROJECTS="clang" \