[try skipping bootstrap-LDC build, use host compiler based on LLVM v17]

Author: kinke

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

@@ -110,7 +110,8 @@ runs:
     - name: Install D host compiler
       uses: dlang-community/setup-dlang@v1
       with:
-        compiler: ldc-latest
+        # macOS arm64: use LDC v1.39.0 using LLVM v17, as Xcode v16
+        compiler: ${{ inputs.arch == 'arm64' && 'ldc-1.39.0' || 'ldc-latest' }}
     - name: 'Posix: Clear LD_LIBRARY_PATH env variable' # don't use host druntime/Phobos .so/.dylib etc.
       if: runner.os != 'Windows'
       shell: bash

.github/workflows/main.yml

@@ -59,10 +59,9 @@ jobs:
               -DD_COMPILER_FLAGS=-gcc=/usr/bin/c++
             extra_cmake_flags: >-
               -DBUILD_LTO_LIBS=ON
-              -DD_COMPILER_FLAGS="-gcc=/usr/bin/c++ -L-exported_symbol '-L__*' -L-w"
-            # -DD_COMPILER_FLAGS="-gcc=/usr/bin/c++ -O -flto=full -defaultlib=phobos2-ldc-lto,druntime-ldc-lto -L-exported_symbol '-L__*' -L-w"
-            #  -DEXTRA_CXXFLAGS="-flto=full -mno-stack-arg-probe -fno-stack-protector"
-            #with_pgo: true
+              -DD_COMPILER_FLAGS="-gcc=/usr/bin/c++ -O -flto=full -defaultlib=phobos2-ldc-lto,druntime-ldc-lto -L-exported_symbol '-L__*' -L-w"
+              -DEXTRA_CXXFLAGS=-flto=full
+            with_pgo: true
 
           - job_name: Windows x64
             os: windows-2022
@@ -105,10 +104,14 @@ jobs:
           llvm_version: ${{ matrix.llvm_version || env.LLVM_VERSION }}
           arch: ${{ matrix.arch }}
       - name: Build bootstrap LDC
+        if: matrix.os != 'macos-14'
         uses: ./.github/actions/2-build-bootstrap
         with:
           cmake_flags: ${{ matrix.bootstrap_cmake_flags }}
           arch: ${{ matrix.arch }}
+      - name: 'macOS 14: Skip bootstrap LDC build'
+        if: matrix.os == 'macos-14'
+        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