chore: Build LLVM for multiple targets

Apart from the x86_64 Linux build, cross compile also to Linux
arm64, macOS x86_64 and macoOS arm64.

.github/workflows/ci.yml

@@ -133,10 +133,10 @@ jobs:
         if: matrix.llvm == 'source'
         run: |
           set -euxo pipefail
-          echo "${{ github.workspace }}/llvm-install/bin" >> $GITHUB_PATH
+          echo "${{ github.workspace }}/llvm-install/x86_64-linux-gnu/bin" >> $GITHUB_PATH
           # LD_LIBRARY_PATH is needed because we're going to link everything dynamically below. This
           # doesn't affect behavior, but greatly reduces disk usage.
-          echo "LD_LIBRARY_PATH=${{ github.workspace }}/llvm-install/lib" >> $GITHUB_ENV
+          echo "LD_LIBRARY_PATH=${{ github.workspace }}/llvm-install/x86_64-linux-gnu/lib" >> $GITHUB_ENV
 
       # llvm-sys discovers link flags at build script time; these are cached by cargo. The cached
       # flags may be incorrect when the cache is reused across LLVM versions.

.github/workflows/llvm.yml

@@ -8,7 +8,18 @@ on:
 
 jobs:
   llvm:
-    runs-on: ubuntu-22.04
+    strategy:
+      matrix:
+        include:
+          - target: aarch64-linux-gnu
+            os: ubuntu-latest
+          - target: aarch64-apple-darwin
+            os: macos-latest
+          - target: x86_64-linux-gnu
+            os: ubuntu-latest
+          - target: x86_64-apple-darwin
+            os: macos-latest
+    runs-on: ${{ matrix.os }}
     name: llvm
     outputs:
       cache-key: ${{ steps.cache-key.outputs.cache-key }}
@@ -30,8 +41,8 @@ jobs:
           key: ${{ steps.cache-key.outputs.cache-key }}
           lookup-only: true
 
-      - name: Install Tools
-        if: steps.cache-llvm.outputs.cache-hit != 'true'
+      - name: Install Tools (Linux)
+        if: steps.cache-llvm.outputs.cache-hit != 'true' && matrix.os == 'ubuntu-latest'
         run: |
           set -euxo pipefail
           wget -O - https://apt.kitware.com/keys/kitware-archive-latest.asc 2>/dev/null | \
@@ -43,6 +54,13 @@ jobs:
           sudo apt update
           sudo apt -y install cmake ninja-build clang lld
 
+      - name: Install Tools (macOS)
+        if: steps.cache-llvm.outputs.cache-hit != 'true' && matrix.os == 'macos-latest'
+        run: |
+          /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
+          echo "/usr/local/bin/brew" >> $GITHUB_PATH
+          brew install cmake ninja
+
       - name: Checkout LLVM Source
         if: steps.cache-llvm.outputs.cache-hit != 'true'
         uses: actions/checkout@v4
@@ -55,22 +73,28 @@ jobs:
         if: steps.cache-llvm.outputs.cache-hit != 'true'
         run: |
           set -euxo pipefail
+          LLVM_USE_LINKER_OPTION=""
+          if [[ "${{ matrix.os }}" == "ubuntu-latest" ]]; then
+            LLVM_USE_LINKER_OPTION="-DLLVM_USE_LINKER=lld"
+          fi
           cmake \
             -S llvm-project/llvm \
             -B llvm-build \
             -G Ninja \
             -DCMAKE_BUILD_TYPE=RelWithDebInfo \
             -DCMAKE_C_COMPILER=clang \
             -DCMAKE_CXX_COMPILER=clang++ \
-            -DCMAKE_INSTALL_PREFIX="${{ github.workspace }}/llvm-install" \
+            -DCMAKE_INSTALL_PREFIX="${{ github.workspace }}/llvm-install/${{ matrix.target }}" \
             -DLLVM_BUILD_LLVM_DYLIB=ON \
+            -DLLVM_DEFAULT_TARGET_TRIPLE=${{ matrix.target }} \
             -DLLVM_ENABLE_ASSERTIONS=ON \
             -DLLVM_ENABLE_PROJECTS= \
             -DLLVM_ENABLE_RUNTIMES= \
+            -DLLVM_HOST_TRIPLE=${{ matrix.target }} \
             -DLLVM_INSTALL_UTILS=ON \
             -DLLVM_LINK_LLVM_DYLIB=ON \
             -DLLVM_TARGETS_TO_BUILD=BPF \
-            -DLLVM_USE_LINKER=lld
+            $LLVM_USE_LINKER_OPTION
 
       - name: Install LLVM
         if: steps.cache-llvm.outputs.cache-hit != 'true'