Disable rust-analyzer tests on LLVM 21

The rust-analyzer tests have been frequently failing with a SIGSEGV on
CI in the LLVM 21 runners. In my investigation, this seems to be fixed
with LLVM 22. It was suggested that we should just disable these tests.

There wasn't a particularly convenient way to detect if this is running
with LLVM 21, so I decided to just check the CI_JOB_NAME which contains
the image name which in our case includes the string "llvm-21".

Fixes #156460

Author: ehuss

src/ci/docker/scripts/stage_2_test_set2.sh

@@ -12,8 +12,18 @@ if [ "$PR_CI_JOB" == "1" ]; then
   SKIP_TIDY="--skip tidy"
 fi
 
+# The combination of rust.randomize-layout and LLVM 21 is causing random
+# SIGSEGV in the `hir-def` rust-analyzer tests. Since it seems to be fixed in
+# LLVM 22, let's just disable this for now since it has been disruptive for
+# CI. See https://github.com/rust-lang/rust/issues/156460.
+if [[ "$CI_JOB_NAME" == *"llvm-21"* ]]; then
+  echo "CI_JOB_NAME contains 'llvm-21'; skipping rust-analyzer"
+  SKIP_RUST_ANALYZER="--skip src/tools/rust-analyzer"
+fi
+
 ../x.py --stage 2 test \
   ${SKIP_TIDY:+$SKIP_TIDY} \
+  ${SKIP_RUST_ANALYZER:+$SKIP_RUST_ANALYZER} \
   --skip tests \
   --skip coverage-map \
   --skip coverage-run \