ci: Test with gnu and musl targets

Then we can ensure we don't end up with a similar issue that happend
with containerd-shim-protos not being buildable with musl on 0.9.0.

Signed-off-by: Fabiano Fidêncio <[email protected]>

Author: fidencio

.github/workflows/ci.yml

@@ -15,14 +15,28 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest]
+        linux-target: [gnu, musl]
+        exclude:
+          - os: macos-latest
+            linux-target: gnu
+          - os: macos-latest
+            linux-target: musl
 
     steps:
       - uses: actions/checkout@v4
 
       - run: ./scripts/install-protobuf.sh
         shell: bash
 
-      - run: rustup toolchain install nightly --component rustfmt
+      - run: |
+          case ${{ matrix.os }} in 
+            macos-latest)
+              rustup toolchain install nightly --component rustfmt
+              ;;
+            ubuntu-latest)
+              rustup toolchain install nightly --component rustfmt --target x86_64-unknown-linux-${{ matrix.linux-target }}
+              ;;
+          esac
       - run: cargo +nightly fmt --all -- --check
 
       # the "runc" and "containerd-shim" crates have `sync` code that is not covered by the workspace