github: Build linux-stage1 and linux in parallel on aarch64 and x86_64

This makes the linux aarch64 package natively built on aarch64,
rather than cross compiled from x86_64.

The linux aarch64 runners currently seem to be faster than the
x86_64 ones - but this change doesn't affect the total pipeline
runtime as the matrices wait for all jobs in them to complete before
proceeding.

Author: mstorsjo

.github/workflows/build.yml

@@ -66,7 +66,13 @@ jobs:
 
   linux-stage1:
     needs: [prepare]
-    runs-on: ubuntu-22.04
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { runner: ubuntu-22.04, arch: x86_64 }
+          - { runner: ubuntu-22.04-arm, arch: aarch64 }
+    runs-on: ${{matrix.runner}}
     steps:
       - uses: actions/checkout@v4
       - name: Build
@@ -91,7 +97,7 @@ jobs:
           tar -Jcf ../$NAME.tar.xz --format=ustar --numeric-owner --owner=0 --group=0 --sort=name --mtime="$BUILD_DATE" $NAME
       - uses: actions/upload-artifact@v4
         with:
-          name: linux-stage1-ucrt-x86_64-toolchain
+          name: linux-stage1-ucrt-${{matrix.arch}}-toolchain
           path: |
             llvm-mingw-*.tar.xz
           retention-days: 7
@@ -129,12 +135,18 @@ jobs:
   # Build a cross compiler for Linux, targeting Windows.
   linux:
     needs: [prepare, linux-stage1, linux-profile]
-    runs-on: ubuntu-22.04
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { runner: ubuntu-22.04, arch: x86_64 }
+          - { runner: ubuntu-22.04-arm, arch: aarch64 }
+    runs-on: ${{matrix.runner}}
     steps:
       - uses: actions/checkout@v4
       - uses: actions/download-artifact@v4
         with:
-          name: linux-stage1-ucrt-x86_64-toolchain
+          name: linux-stage1-ucrt-${{matrix.arch}}-toolchain
       - name: Unpack stage1 Clang
         run: |
           tar -Jxf llvm-mingw-*.tar.xz
@@ -164,59 +176,7 @@ jobs:
           tar -Jcf ../$NAME.tar.xz --format=ustar --numeric-owner --owner=0 --group=0 --sort=name --mtime="$BUILD_DATE" $NAME
       - uses: actions/upload-artifact@v4
         with:
-          name: linux-ucrt-x86_64-toolchain
-          path: |
-            llvm-mingw-*.tar.xz
-          retention-days: 7
-
-  # Crosscompile the toolchain for running on Linux on a different architecture, bundle the runtime
-  # libraries that were built in the 'linux-stage1' step above.
-  linux-cross-aarch64:
-    needs: [linux-stage1, linux-profile, prepare]
-    runs-on: ubuntu-22.04
-    steps:
-      - uses: actions/checkout@v4
-      - uses: actions/download-artifact@v4
-        with:
-          name: linux-stage1-ucrt-x86_64-toolchain
-      - name: Unpack stage1 Clang
-        run: |
-          tar -Jxf llvm-mingw-*.tar.xz
-          rm llvm-mingw-*.tar.xz
-          sudo mv llvm-mingw* /opt/llvm-mingw
-      - uses: actions/download-artifact@v4
-        with:
-          name: profile
-      - name: Build
-        env:
-          LLVM_VERSION: ${{needs.prepare.outputs.LLVM_VERSION}}
-          MINGW_W64_VERSION: ${{needs.prepare.outputs.MINGW_W64_VERSION}}
-          SOURCE_DATE_EPOCH: ${{needs.prepare.outputs.COMMIT_DATE_UNIX}}
-        run: |
-          sudo apt-get update && sudo apt-get install g++-aarch64-linux-gnu
-          ./build-all.sh /opt/llvm-mingw $(pwd)/install/llvm-mingw --no-runtimes --host=aarch64-linux-gnu --thinlto --pgo
-          .github/workflows/store-version.sh install/llvm-mingw/versions.txt
-      - name: Assemble the cross-built toolchain
-        run: |
-          ./prepare-cross-toolchain-unix.sh /opt/llvm-mingw $(pwd)/install/llvm-mingw
-      - name: Test using the cross-built assembled toolchain
-        run: |
-          sudo apt-get update && sudo apt-get install qemu-user-static libc6-arm64-cross libstdc++6-arm64-cross
-          QEMU_LD_PREFIX=/usr/aarch64-linux-gnu ./test-libcxx-module.sh $(pwd)/install/llvm-mingw
-          QEMU_LD_PREFIX=/usr/aarch64-linux-gnu ./run-tests.sh $(pwd)/install/llvm-mingw
-      - name: Package the toolchain
-        env:
-          TAG: ${{needs.prepare.outputs.TAG}}
-          BUILD_DATE: ${{needs.prepare.outputs.BUILD_DATE}}
-        run: |
-          cd install
-          DISTRO=ubuntu-$(grep DISTRIB_RELEASE /etc/lsb-release | cut -f 2 -d =)-aarch64
-          NAME=llvm-mingw-$TAG-ucrt-$DISTRO
-          mv llvm-mingw $NAME
-          tar -Jcf ../$NAME.tar.xz --format=ustar --numeric-owner --owner=0 --group=0 --sort=name --mtime="$BUILD_DATE" $NAME
-      - uses: actions/upload-artifact@v4
-        with:
-          name: linux-ucrt-aarch64-toolchain
+          name: linux-ucrt-${{matrix.arch}}-toolchain
           path: |
             llvm-mingw-*.tar.xz
           retention-days: 7
@@ -787,7 +747,7 @@ jobs:
     if: github.event_name == 'schedule'
     permissions:
       contents: write
-    needs: [linux, linux-cross-aarch64, macos, linux-cross-windows, test-toolchain, linux-test-cross-build-ffmpeg, test-ffmpeg]
+    needs: [linux, macos, linux-cross-windows, test-toolchain, linux-test-cross-build-ffmpeg, test-ffmpeg]
     runs-on: ubuntu-latest
     steps:
       - name: Download all artifacts