commit d166f03f254823004a08a927027a77b2ee5ee31a
Author: Arran Ubels <arran4@gmail.com>
Date: Fri Sep 25 11:27:50 2026 +0000

dev-lang/flutter: add genuine source-built Flutter 3.47.2 package and virtual/flutter

Add genuine source-built dev-lang/flutter 3.47.2 integrated with the
source-built dev-libs/flutter-engine-3.47.2 and virtual/dart-3.13.3-r1.

Key design & packaging aspects:
- Tooling snapshot compilation: Pins and declares all 101 pub dependencies
required for packages/flutter_tools, caching them in .pub-cache to compile
flutter_tools.snapshot offline without network access at emerge time.
- Engine wiring: Reuses Engine artifacts directly from /usr/lib/flutter-engine/3.47.2
via package-managed symlinks into /opt/flutter/bin/cache, avoiding payload
duplication while supplying debug/profile/release binaries and product patched SDKs.
- Wrapper & offline runtime: Reuses and adapts XDG cache wrapper and patches
flutter_tools to prevent runtime downloads of official SDK binaries or precache
artifacts.
- Blocker & virtual: Introduces virtual/flutter-3.47.2 allowing either source or
binary provider, bumps flutter-bin to -r1, and enforces mutual exclusivity via
blockers (!dev-lang/flutter-bin / !dev-lang/flutter).
- Testing & verification: Adds scripts/generate_flutter_ebuild.py generator and
scripts/test_generate_flutter_ebuild.py unit tests, scripts/test_flutter_source.sh
containerized integration script, and GitHub Actions CI workflow.

Closes #934