Fix CI.

.github/workflows/clang.yml

@@ -18,7 +18,6 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest]
         std_version: [20, 23]
-        clang_version: [17, 18]
 
     steps:
       - name: Checkout
@@ -31,24 +30,26 @@ jobs:
 
       - name: Get LLVM and Ninja via Homebrew
         run: |
-          brew install llvm@${{ matrix.clang_version }} ninja
+          brew install llvm ninja
 
       - name: Make local build of libc++ with module enabled
         run: |
           git clone https://github.com/llvm/llvm-project.git
           cd llvm-project
           mkdir build
-          cmake -G Ninja -S runtimes -B build \
+          CC=$(brew --prefix llvm)/bin/clang                    \
+          CXX=$(brew --prefix llvm)/bin/clang++                 \
+          cmake -G Ninja -S runtimes -B build                   \
             -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind"
           ninja -C build
-          cd ../
 
       - name: Configure
         run: |
           mkdir build
-          CXX=$(brew --prefix llvm@${{ matrix.clang_version }})/bin/clang++ \
-          cmake -S . -G "Ninja" -B build \
-            -DCMAKE_CXX_STANDARD=${{ matrix.std_version }} \
+          CC=$(brew --prefix llvm)/bin/clang                          \
+          CXX=$(brew --prefix llvm)/bin/clang++                       \
+          cmake -S . -G Ninja -B build                                \
+            -DCMAKE_CXX_STANDARD=${{ matrix.std_version }}            \
             -DLIBCXX_BUILD=${{ github.workspace }}/llvm-project/build
 
       - name: Build