.github: run ci on net and freebsd too

.github/workflows/ci.yaml

@@ -86,18 +86,32 @@ jobs:
       run: |
         ninja -C /tmp/build
 
-  build-openbsd:
+  build-cross:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        os:
+        - name: freebsd
+          version: '13.2'
+          install_cmd: pkg install -fy
+        - name: openbsd
+          version: '7.3'
+          install_cmd: pkg_add
+        - name: netbsd
+          version: '9.3'
+          install_cmd: >-
+            PKG_PATH=https://cdn.netbsd.org/pub/pkgsrc/packages/NetBSD/x86_64/9.3/All/
+            /usr/pkg/sbin/pkg_add
     steps:
     - uses: actions/checkout@v3
     - uses: "cross-platform-actions/action@v0.15.0"
       continue-on-error: true
       with:
-        operating_system: openbsd
+        operating_system: ${{ matrix.os.name }}
         architecture: x86-64
-        version: 7.2
+        version: ${{ matrix.os.version }}
         run: |
-          sudo pkg_add git meson squashfs-tools curl lz4 xz zstd
+          sudo ${{ matrix.os.install_cmd }} git meson squashfs-tools curl lz4 xz zstd
           CC=clang meson setup /tmp/build \
             -Dwerror=true \
             -Dcurl=enabled \
@@ -115,7 +129,7 @@ jobs:
   doxygen:
     needs:
     - build
-    - build-openbsd
+    - build-cross
     - plain-build
     - test
     runs-on: ubuntu-latest