ci: Run integration tests on Alpine

This way we are making sure that the integration tests infra doesn't
regress on musl environments.

.github/workflows/ci.yml

@@ -202,19 +202,69 @@ jobs:
           - target: x86_64-unknown-linux-gnu
             # We don't use ubuntu-latest because we care about the apt packages available.
             os: ubuntu-22.04
+          - target: x86_64-unknown-linux-musl
+            os: ubuntu-22.04
+            container:
+              image: docker.io/alpine:3.20
+              options: --privileged -v /sys/fs/bpf:/sys/fs/bpf -v /sys/kernel:/sys/kernel
     runs-on: ${{ matrix.os }}
+    container: ${{ matrix.container }}
     steps:
-      - uses: actions/checkout@v4
-        with:
-          submodules: recursive
+      - name: Install prerequisites
+        if: runner.os == 'Linux' && contains(matrix.container.image, 'alpine')
+        # bash is used in the `rust-toolchain` action.
+        #
+        # clang and make are needed for building the C eBPF programs, which are
+        # part of the integration tests.
+        #
+        # curl, file and jq are used in the steps below.
+        #
+        # dpkg is used to unpack the kernel images from .deb packages, which we
+        # use for virtualized tests. lynx is used to download them.
+        #
+        # gcc is needed as a linker, it also provides the runtime library, both
+        # needed by Rust.
+        #
+        # git is needed for the `checkout` action.
+        #
+        # libstdc++ is a dependency of llvm-sys, which is a dependency of
+        # bpf-linker.
+        #
+        # musl-dev provides CRT objects, which are linked by Rust.
+        #
+        # QEMU is used to run virtualized integration tests.
+        #
+        # sudo is needed by integration tests.
+        run: |
+          set -euxo pipefail
+          apk add \
+            bash \
+            clang \
+            curl \
+            dpkg \
+            file \
+            gcc \
+            git \
+            jq \
+            libstdc++-dev \
+            lynx \
+            make \
+            musl-dev \
+            qemu-system-arm \
+            qemu-system-x86_64 \
+            sudo
 
       - name: Install prerequisites
-        if: runner.os == 'Linux'
+        if: runner.os == 'Linux' && matrix.container == ''
         # ubuntu-22.04 comes with clang 13-15[0]; support for signed and 64bit
         # enum values was added in clang 15[1] which isn't in `$PATH`.
         #
         # gcc-multilib provides at least <asm/types.h> which is referenced by libbpf.
         #
+        # lynx is used to download kernel images.
+        #
+        # QEMU is used to run virtualized integration tests.
+        #
         # [0] https://github.com/actions/runner-images/blob/main/images/ubuntu/Ubuntu2204-Readme.md
         #
         # [1] https://github.com/llvm/llvm-project/commit/dc1c43d
@@ -224,6 +274,26 @@ jobs:
           sudo apt -y install gcc-multilib lynx qemu-system-{arm,x86}
           echo /usr/lib/llvm-15/bin >> $GITHUB_PATH
 
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      # When running in a container as root, git throws the following error:
+      #
+      # fatal: detected dubious ownership in repository at '/__w/aya/aya'
+      #
+      # Which makes a lot of sense, not running regular git commands as root is
+      # a good thing. However, using a container image with a regular user
+      # results in permission errors thrown by the runner binary.[0] It's most
+      # likely because of a host volume mount which is owned by root. It would
+      # be great to make it work, but it's not going to be trivial and might
+      # require changes in the runner code itself.
+      #
+      # [0] https://github.com/aya-rs/aya/actions/runs/12034434029/job/33550963904
+      - name: Mark the directory as safe for git
+        if: matrix.container != ''
+        run: git config --global --add safe.directory /__w/aya/aya
+
       - name: Install prerequisites
         if: runner.os == 'macOS'
         # The xargs shipped on macOS always exits 0 with -P0, so we need GNU findutils.