[clang] [libc] [llvm] [libc][Github] Perform baremetal libc builds (PR #167583)

[Petr Hosek via llvm-commits]

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@@ -93,28 +129,38 @@ jobs:
       run: |
         export RUNTIMES="libc"
 
+        export CMAKE_FLAGS="
+          -G Ninja
+          -S ${{ github.workspace }}/runtimes
+          -B ${{ steps.strings.outputs.build-output-dir }}
+          -DCMAKE_CXX_COMPILER=${{ matrix.cpp_compiler }}
+          -DCMAKE_C_COMPILER=${{ matrix.c_compiler }}
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petrhosek wrote:

We should be also setting `CMAKE_ASM_COMPILER` for any `.S` files to avoid using the host compiler.

https://github.com/llvm/llvm-project/pull/167583