fix: Use full paths for LLVM 18 tools in workflow steps

The llvm-18-tools package installs tools in /usr/lib/llvm-18/bin/, not
/usr/bin/. Environment variables and symlinks don't reliably carry over
between GitHub Actions job steps.

Solution: Use absolute paths (/usr/lib/llvm-18/bin/llvm-profdata, etc.)
directly in all workflow steps where LLVM tools are called. Still create
symlinks in /usr/bin for scripts that expect the tools to be in PATH.

This ensures LLVM tools are found regardless of how the shell is invoked
or what environment variables are set in different job steps.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Haiku 4.5 <[email protected]>

Author: cdecker

.github/workflows/coverage-nightly.yaml

@@ -44,7 +44,7 @@ jobs:
           echo "Recording LLVM version used for compilation..."
           clang-18 --version > LLVM_VERSION.txt
           echo "" >> LLVM_VERSION.txt
-          llvm-profdata-18 --version >> LLVM_VERSION.txt
+          /usr/lib/llvm-18/bin/llvm-profdata --version >> LLVM_VERSION.txt
           cat LLVM_VERSION.txt
           tar -rf testpack.tar.bz2 LLVM_VERSION.txt
 
@@ -148,7 +148,7 @@ jobs:
             echo ""
             echo "Current system LLVM version:"
             clang-18 --version
-            llvm-profdata-18 --version
+            /usr/lib/llvm-18/bin/llvm-profdata --version
           else
             echo "⚠ WARNING: LLVM_VERSION.txt not found in build artifact"
           fi
@@ -190,10 +190,9 @@ jobs:
         if: always()
         run: |
           echo "Verifying LLVM 18 tools are available..."
-          which llvm-profdata-18
-          llvm-profdata-18 --version
+          /usr/lib/llvm-18/bin/llvm-profdata --version
           # Create symlinks for scripts that expect llvm-profdata without version suffix
-          sudo ln -sf /usr/bin/llvm-profdata-18 /usr/bin/llvm-profdata || true
+          sudo ln -sf /usr/lib/llvm-18/bin/llvm-profdata /usr/bin/llvm-profdata || true
 
       - name: Merge coverage data locally
         if: always()
@@ -234,13 +233,11 @@ jobs:
       - name: Verify LLVM tools are available
         run: |
           echo "Verifying LLVM 18 tools are available..."
-          which llvm-profdata-18
-          which llvm-cov-18
-          llvm-profdata-18 --version
-          llvm-cov-18 --version
+          /usr/lib/llvm-18/bin/llvm-profdata --version
+          /usr/lib/llvm-18/bin/llvm-cov --version
           # Create symlinks for scripts that expect tools without version suffix
-          sudo ln -sf /usr/bin/llvm-profdata-18 /usr/bin/llvm-profdata || true
-          sudo ln -sf /usr/bin/llvm-cov-18 /usr/bin/llvm-cov || true
+          sudo ln -sf /usr/lib/llvm-18/bin/llvm-profdata /usr/bin/llvm-profdata || true
+          sudo ln -sf /usr/lib/llvm-18/bin/llvm-cov /usr/bin/llvm-cov || true
 
       - name: Download build artifact
         uses: actions/download-artifact@v4
@@ -258,7 +255,7 @@ jobs:
             cat LLVM_VERSION.txt
             echo ""
             echo "Current system LLVM version:"
-            llvm-profdata-18 --version
+            /usr/lib/llvm-18/bin/llvm-profdata --version
             echo ""
             echo "✓ LLVM version verification complete"
           else