try the mac os thing

.github/workflows/main.yml

@@ -37,7 +37,7 @@ jobs:
             with_pgo: false
 
           - job_name: macOS x86_64
-            os: macos-12
+            os: macos-13
             arch: x86_64
             bootstrap_cmake_flags: >-
               -DBUILD_LTO_LIBS=ON
@@ -79,10 +79,14 @@ jobs:
           llvm_version: ${{ env.LLVM_VERSION }}
           arch: ${{ matrix.arch }}
       - name: Build bootstrap LDC
+        if: matrix.os != 'macos-15'
         uses: ./.github/actions/2-build-bootstrap
         with:
           cmake_flags: ${{ matrix.bootstrap_cmake_flags }}
           arch: ${{ matrix.arch }}
+      - name: 'macOS 15: Use host LDC (with Xcode-compatible LLVM version) as bootstrap LDC'
+        if: matrix.os == 'macos-15'
+        run: ln -s $(dirname $(dirname $(which ldmd2))) ../bootstrap-ldc
       - name: Build LDC with PGO instrumentation & gather profile from compiling default libs
         if: matrix.with_pgo
         uses: ./.github/actions/2a-build-pgo
@@ -126,7 +130,7 @@ jobs:
         include:
 
           - job_name: macOS arm64
-            host_os: macos-12
+            host_os: macos-15
             os: osx
             arch: arm64
             bootstrap_cmake_flags: -DD_COMPILER_FLAGS=-gcc=/usr/bin/c++