build: Install flutter via git in snapcraft

snap/snapcraft.yaml

@@ -61,18 +61,41 @@ parts:
     build-packages:
       - g++
 
+  flutter-git:
+    source: https://github.com/flutter/flutter.git
+    source-tag: 3.27.4
+    plugin: nil
+    override-build: |
+      set -eux
+      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 -sf $CRAFT_PART_INSTALL/usr/libexec/flutter/bin/flutter $CRAFT_PART_INSTALL/usr/bin/flutter
+      export PATH="$CRAFT_PART_INSTALL/usr/bin:$PATH"
+      flutter doctor
+    build-packages:
+      - clang
+      - cmake
+      - curl
+      - ninja-build
+      - unzip
+    override-prime: ''
+
   fluffychat:
-    plugin: flutter
+    after: [ flutter-git ]
+    plugin: nil
     source: .
     override-build: |
-      # Workaround for Flutter build error:
-      rm -rf build
-      craftctl default
+      flutter pub get || true
+      flutter build linux --release -v
+      mkdir -p $CRAFT_PART_INSTALL/bin
+      cp -r build/linux/*/release/bundle/* $CRAFT_PART_INSTALL/bin/
     build-packages:
       - libsecret-1-dev
       - libjsoncpp-dev
       - libssl-dev
       - curl
+      - jq
     stage-packages:
       - libsecret-1-0
       - libjsoncpp25
@@ -85,7 +108,7 @@ slots:
 
 apps:
   fluffychat:
-    command: fluffychat
+    command: bin/fluffychat
     extensions: [ gnome ]
     plugs:
       - audio-playback