ci: run MSan on arm64

Add a debug-arm64 matrix entry to the test job that runs the MSan
fuzz tests on an arm64 runner. The arm instrumented libc++ toolchain
(22.1.8) is built against LLVM 22, so this entry installs clang-22
from apt.llvm.org while the existing amd64 entries keep clang-21.

Generalize the test job matrix with runner/arch/llvm_version/msan_url
fields so the runner, apt cache key, LLVM toolchain version, and MSan
toolchain download URL are selected per matrix entry.

Closes #73

.gitea/workflows/ci.yml

@@ -38,21 +38,43 @@ jobs:
       matrix:
         include:
           - name: 64-bit-versions
+            runner: ubuntu-latest-amd64
+            arch: amd64
+            llvm_version: "21"
+            msan_url: ""
             cmake_args: -DCMAKE_CXX_FLAGS=-DUSE_64_BIT=1
           - name: debug
+            runner: ubuntu-latest-amd64
+            arch: amd64
+            llvm_version: "21"
+            msan_url: https://minio.weaselab.dev/public/x86_64/msan-toolchain-21.1.8.tar.zst
             cmake_args: -DCMAKE_BUILD_TYPE=Debug -DMSAN_TOOLCHAIN_PATH=/opt/msan
           - name: simd-fallback
+            runner: ubuntu-latest-amd64
+            arch: amd64
+            llvm_version: "21"
+            msan_url: ""
             cmake_args: -DUSE_SIMD_FALLBACK=ON
           - name: gcc
+            runner: ubuntu-latest-amd64
+            arch: amd64
+            llvm_version: "21"
+            msan_url: ""
             cmake_args: -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++
-    runs-on: ubuntu-latest-amd64
+          - name: debug-arm64
+            runner: ubuntu-latest-arm64
+            arch: arm64
+            llvm_version: "22"
+            msan_url: https://minio.weaselab.dev/public/aarch64/msan-toolchain-22.1.8.tar.zst
+            cmake_args: -DCMAKE_BUILD_TYPE=Debug -DMSAN_TOOLCHAIN_PATH=/opt/msan
+    runs-on: ${{ matrix.runner }}
     steps:
       - uses: actions/checkout@v4
 
       - uses: actions/cache@v4
         with:
           path: /var/cache/apt/archives
-          key: apt-amd64-${{ hashFiles('.gitea/workflows/ci.yml') }}
+          key: apt-${{ matrix.arch }}-${{ hashFiles('.gitea/workflows/ci.yml') }}
 
       - name: Install common dependencies
         run: |
@@ -68,18 +90,18 @@ jobs:
         run: |
           . /etc/os-release
           wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
-          echo "deb http://apt.llvm.org/${VERSION_CODENAME}/ llvm-toolchain-${VERSION_CODENAME}-21 main" | sudo tee /etc/apt/sources.list.d/llvm.list
+          echo "deb http://apt.llvm.org/${VERSION_CODENAME}/ llvm-toolchain-${VERSION_CODENAME}-${{ matrix.llvm_version }} main" | sudo tee /etc/apt/sources.list.d/llvm.list
           sudo apt-get update -qq
           sudo apt-get install -y \
-            clang-21 llvm-21 lld-21 mold
+            clang-${{ matrix.llvm_version }} llvm-${{ matrix.llvm_version }} lld-${{ matrix.llvm_version }} mold
           for tool in clang clang++ llvm-ar llvm-nm llvm-ranlib llvm-objcopy llvm-cov llvm-symbolizer lld ld.lld; do
-            sudo update-alternatives --install /usr/bin/${tool} ${tool} /usr/bin/${tool}-21 100
+            sudo update-alternatives --install /usr/bin/${tool} ${tool} /usr/bin/${tool}-${{ matrix.llvm_version }} 100
           done
 
       - name: Download MSan toolchain
-        if: matrix.name == 'debug'
+        if: matrix.msan_url != ''
         run: |
-          curl -Ls "https://minio.weaselab.dev/public/x86_64/msan-toolchain-21.1.8.tar.zst" -o /tmp/msan-toolchain.tar.zst
+          curl -Ls "${{ matrix.msan_url }}" -o /tmp/msan-toolchain.tar.zst
           sudo mkdir -p /opt/msan
           sudo tar --zstd -xf /tmp/msan-toolchain.tar.zst -C /opt/msan