r-g/flutter-apps: Fix lib path in flutter-gallery

Fix homescreen in release mode

Relate-to: #3
Relate-to: https://booting.oniroproject.org/rzr/meta-oniro-blueprint-flutter/-/issues/3#note_24362
Relate-to: https://github.com/meta-flutter/meta-flutter/pull/123


Signed-off-by: Philippe Coval <philippe.coval.ext@huawei.com>