[macOS tweaks]

Author: kinke

.github/actions/1-setup/action.yml

@@ -35,6 +35,31 @@ runs:
         sudo ln -sf ld.lld-21 /usr/bin/ld
         ld --version
 
+    - name: 'macOS: Install Homebrew clang 21'
+      if: runner.os == 'macOS'
+      shell: bash
+      run: |
+        set -eux
+        brew install llvm@21
+
+        if [[ '${{ inputs.arch }}' == arm64 ]]; then
+          prefix="/opt/homebrew/opt/llvm"
+        else
+          prefix="/usr/local/opt/llvm"
+        fi
+
+        # use it as C(++) compiler for future steps
+        echo "CC=$prefix/bin/clang" >> $GITHUB_ENV
+        echo "CXX=$prefix/bin/clang++" >> $GITHUB_ENV
+
+        # https://github.com/actions/runner-images/issues/10035#issue-2344536514
+        sudo xcode-select -s /Library/Developer/CommandLineTools
+        xcrun --show-sdk-path
+        ls -l /Library/Developer/CommandLineTools/SDKs
+
+        # https://github.com/llvm/llvm-project/issues/155531#issuecomment-3229499205
+        rm -rf "$prefix/include/c++/v1"
+
     - name: 'Windows: Install clang 21 from GitHub'
       if: runner.os == 'Windows'
       shell: bash

.github/workflows/ldc-release.yml

@@ -76,11 +76,11 @@ jobs:
             arch: arm64
             with_asserts: true
           - job_name: macOS x86_64
-            os: macos-13
+            os: macos-15-intel
             arch: x86_64
             with_asserts: false
           - job_name: macOS x86_64 withAsserts
-            os: macos-13
+            os: macos-15-intel
             arch: x86_64
             with_asserts: true
     name: ${{ matrix.job_name }}