add GitHub Actions workflow for cross-platform Flutter builds

Author: benginsternas

.github/workflows/build.yml

@@ -0,0 +1,117 @@
+name: Build and Release
+
+on:
+  push:
+    branches: [ "main" ]
+  workflow_dispatch:
+
+jobs:
+  build-windows:
+    name: Build Windows ${{ matrix.arch }}
+    runs-on: windows-latest
+    strategy:
+      matrix:
+        arch: [x64, arm64]
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Setup Flutter
+        uses: subosito/flutter-action@v2
+        with:
+          channel: 'stable'
+          cache: true
+
+      - name: Install dependencies
+        run: flutter pub get
+
+      - name: Build Windows
+        run: |
+          if ("${{ matrix.arch }}" -eq "arm64") {
+            flutter build windows --target-platform windows-arm64
+          } else {
+            flutter build windows
+          }
+
+      - name: Package Windows Artifact
+        shell: pwsh
+        run: |
+          $version = (Get-Content pubspec.yaml | Select-String "version: " | ForEach-Object { $_.ToString().Split(": ")[1].Trim() })
+          $folder = "build/windows/x64/runner/Release"
+          if ("${{ matrix.arch }}" -eq "arm64") {
+            $folder = "build/windows/arm64/runner/Release"
+          }
+          Compress-Archive -Path "$folder/*" -DestinationPath "belegium_${version}_windows_${{ matrix.arch }}.zip"
+
+      - name: Upload Artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: windows-${{ matrix.arch }}-build
+          path: "*.zip"
+
+  build-macos:
+    name: Build macOS (Universal)
+    runs-on: macos-latest
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Setup Flutter
+        uses: subosito/flutter-action@v2
+        with:
+          channel: 'stable'
+          cache: true
+
+      - name: Install dependencies
+        run: flutter pub get
+
+      - name: Build macOS
+        run: flutter build macos
+
+      - name: Package macOS Artifact
+        run: |
+          VERSION=$(grep 'version: ' pubspec.yaml | sed 's/version: //')
+          APP_PATH="build/macos/Build/Products/Release/belegium.app"
+          ditto -c -k --sequesterRsrc --keepParent "$APP_PATH" "belegium_${VERSION}_macos_universal.zip"
+
+      - name: Upload Artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: macos-build
+          path: "*.zip"
+
+  build-linux:
+    name: Build Linux
+    runs-on: ubuntu-latest
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Install Linux dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libgtk-3-dev libblkid-dev liblzma-dev ninja-build pkg-config
+
+      - name: Setup Flutter
+        uses: subosito/flutter-action@v2
+        with:
+          channel: 'stable'
+          cache: true
+
+      - name: Install dependencies
+        run: flutter pub get
+
+      - name: Build Linux
+        run: flutter build linux
+
+      - name: Package Linux Artifact
+        run: |
+          VERSION=$(grep 'version: ' pubspec.yaml | sed 's/version: //')
+          cd build/linux/x64/release/bundle
+          tar -czvf "../../../../../belegium_${VERSION}_linux_x64.tar.gz" .
+
+      - name: Upload Artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: linux-build
+          path: "*.tar.gz"