build: Use Flutter 3.19.6 for Linux

snap/snapcraft.yaml

@@ -64,13 +64,40 @@ parts:
     stage-snaps:
       - zenity-integration
 
+  flutter-git:
+    source: https://github.com/flutter/flutter.git
+    source-tag: 3.19.6
+    source-depth: 1
+    plugin: nil
+    override-build: |
+      mkdir -p $CRAFT_PART_INSTALL/usr/bin
+      mkdir -p $CRAFT_PART_INSTALL/usr/libexec
+      cp -r $CRAFT_PART_SRC $CRAFT_PART_INSTALL/usr/libexec/flutter
+      ln -s $CRAFT_PART_INSTALL/usr/libexec/flutter/bin/flutter $CRAFT_PART_INSTALL/usr/bin/flutter
+      ln -s $SNAPCRAFT_PART_INSTALL/usr/libexec/flutter/bin/dart $SNAPCRAFT_PART_INSTALL/usr/bin/dart
+      $CRAFT_PART_INSTALL/usr/bin/flutter doctor
+    build-packages:
+      - clang
+      - cmake
+      - curl
+      - libgtk-3-dev
+      - ninja-build
+      - unzip
+      - xz-utils
+      - zip
+    override-prime: ''
+
   fluffychat:
-    plugin: flutter
+    after: [flutter-git]
+    plugin: nil
     source: .
     override-build: |
       # Workaround for Flutter build error:
       rm -rf build
-      craftctl default
+
+      flutter build linux --release -v
+      mkdir -p $CRAFT_PART_INSTALL/bin/
+      cp -r build/linux/*/release/bundle/* $CRAFT_PART_INSTALL/bin/
     build-packages:
       - libjsoncpp-dev
       - curl
@@ -87,7 +114,7 @@ slots:
 
 apps:
   fluffychat:
-    command: fluffychat
+    command: bin/fluffychat
     extensions: [ gnome ]
     plugs:
       - audio-playback