Add Amiga workflow

.github/workflows/amiga.yml

@@ -0,0 +1,58 @@
+name: amiga
+
+on: [push, pull_request, workflow_dispatch]
+
+concurrency:
+  group: ${{github.workflow}}-${{github.event.pull_request.number || github.ref}}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  package:
+    runs-on: ubuntu-latest
+    timeout-minutes: 120
+    steps:
+      - uses: actions/checkout@v4
+
+      # Ubuntu's `lha` package is lhasa: extract-only, cannot create archives.
+      # Build LHa for UNIX (https://github.com/jca02266/lha) instead.
+      - name: Install LHa for UNIX
+        working-directory: ${{runner.temp}}
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y autoconf automake
+          curl -fsSL -o lha.tar.gz \
+            https://github.com/jca02266/lha/archive/16619b066b189ef289bb8b07b37d1c38d550da99.tar.gz
+          tar -xzf lha.tar.gz
+          cd lha-16619b066b189ef289bb8b07b37d1c38d550da99
+          autoreconf -is
+          ./configure --prefix="$HOME/.local"
+          make -j"$(nproc)"
+          make install
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+
+      - name: Check lha can create archives
+        run: |
+          command -v lha
+          d=$(mktemp -d)
+          echo probe > "$d/f"
+          ( cd "$d" && lha -aq2 t.lha f )
+          test -s "$d/t.lha"
+
+      - name: Pull compiler images
+        run: |
+          docker pull sacredbanana/amiga-compiler:m68k-amigaos &
+          docker pull sacredbanana/amiga-compiler:ppc-amigaos &
+          docker pull sacredbanana/amiga-compiler:ppc-morphos &
+          wait
+
+      - name: Build and package
+        run: ./package-amiga.sh
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: json-c.lha
+          path: dist/json-c.lha
+          if-no-files-found: error