feat: build llvm in docker

Author: simonresch

.github/workflows/build-llvm.yaml

@@ -9,30 +9,51 @@ on:
         type: string
 
 jobs:
-  build_llvm:
+  build_llvm_mac:
+    name: Build LLVM
+    runs-on: macos-14
+    steps:
+      - name: checkout
+        uses: actions/checkout@v3
+      - run: "brew install ninja"
+      # Build and package LLVM.
+      - run: "./build-llvm-libs.sh llvm-static-libs-macos-14.tar.gz"
+      - uses: actions/upload-artifact@v4
+        with:
+          name: llvm-static-libs-macos-14
+          path: llvm-static-libs-macos-14.tar.gz
+
+  build_llvm_linux:
     name: Build LLVM
     strategy:
       matrix:
-        os: [ubuntu-20.04, ubuntu-24.04-arm, macos-14]
+        os: [ubuntu-24.04, ubuntu-24.04-arm]
     runs-on: ${{ matrix.os }}
+    container: ubuntu:20.04
+    env:
+      DEBIAN_FRONTEND: noninteractive
     steps:
       - name: checkout
         uses: actions/checkout@v3
-      - if: contains(matrix.os, 'ubuntu')
-        run: "sudo apt update && sudo apt install -y ninja-build"
-      - if: contains(matrix.os, 'macos')
-        run: "brew install ninja"
+      - run: "apt update && apt install -y ninja-build gcc g++ git wget"
+      # Install recent CMake.
+      - run: |
+          export ARCH=${{ runner.arch == 'x64' && 'x86_64' || 'aarch64' }}
+          wget https://github.com/Kitware/CMake/releases/download/v3.31.5/cmake-3.31.5-linux-$ARCH.sh -O cmake-install.sh
+          chmod +x cmake-install.sh
+          ./cmake-install.sh --skip-license --prefix=/usr/local
+          rm cmake-install.sh
       # Build and package LLVM.
-      - run: "./build-llvm-libs.sh llvm-static-libs-${{ matrix.os }}.tar.gz"
+      - run: "./build-llvm-libs.sh llvm-static-libs-ubuntu-20.04-${{ runner.arch }}.tar.gz"
       - uses: actions/upload-artifact@v4
         with:
-          name: llvm-static-libs-${{ matrix.os }}
-          path: llvm-static-libs-${{ matrix.os }}.tar.gz
+          name: llvm-static-libs-ubuntu-20.04-${{ runner.arch }}
+          path: llvm-static-libs-ubuntu-20.04-${{ runner.arch }}.tar.gz
 
   create_release:
     name: Create release
     runs-on: ubuntu-latest
-    needs: [build_llvm]
+    needs: [build_llvm_mac, build_llvm_linux]
     permissions:
       contents: write # for creating releases
     steps:

build-llvm-libs.sh

@@ -10,9 +10,6 @@ then
   OUTPUT_FILE=$1
 fi
 
-CC=clang
-CXX=clang++
-
 ARCH=$(uname -m)
 
 if [ "$ARCH" == "x86_64" ]; then