WIP: github: Run test-llvm with a specific commit

This commit fixes the last known crash in dsymutil.

Author: mstorsjo

.github/workflows/test-llvm.yml

@@ -73,7 +73,7 @@ jobs:
       - uses: actions/checkout@v4
       - name: Checkout llvm-project
         env:
-          LLVM_VERSION: ${{needs.prepare.outputs.LLVM_VERSION}}
+          LLVM_VERSION: 52f568dbbb61ffe26b7973b482e0e504b405a0ab
         run: |
           git config --global core.autocrlf false
           bash -c "CHECKOUT_ONLY=1 ./build-llvm.sh"