clang version diag

Author: rscharfe

.github/workflows/main.yml

@@ -115,7 +115,7 @@ jobs:
       matrix:
         vector:
           - jobname: osx-clang
-            cc: /opt/homebrew/opt/llvm@15/bin/clang
+            cc: /opt/homebrew/opt/llvm/bin/clang
             pool: macos-14
           - jobname: osx-reftable
             cc: clang
@@ -130,6 +130,7 @@ jobs:
     steps:
     - uses: actions/checkout@v5
     - run: ci/install-dependencies.sh
+    - run: printf "%s\n" "#include <regex.h>" REG_ENHANCED __MAC_OS_X_VERSION_MIN_REQUIRED | /opt/homebrew/opt/llvm@15/bin/clang -E -
     - run: ci/run-build-and-tests.sh
     - name: print test failures
       if: failure() && env.FAILED_TEST_ARTIFACTS != ''