[CI] Add missing libunwind

Author: banach-space

.github/workflows/apple-silicon-llvm-from-sources.yml

@@ -29,7 +29,7 @@ jobs:
           mkdir build && cd build
           cmake -G Ninja \
             -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang" \
-            -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi" \
+            -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind" \
             -DLLVM_TARGETS_TO_BUILD="host" \
             -DLLVM_OPTIMIZED_TABLEGEN=ON \
             -DDEFAULT_SYSROOT="$(xcrun --show-sdk-path)" \