app, configure: adding dependency to mypaint-brushes.
This ensures that MyPaint default brushes are installed, otherwise this makes the MyPaint brush tool quite useless and confusing unless MyPaint is installed (which was making MyPaint a de-facto dependency of GIMP until this commit!). Also we won't have to guess anymore the right path for these brushs. The path will be known at compile time.
Showing with 4 additions and 23 deletions