[vfx][build] fix API Makefile to descent properly to 'vfx/' dir.
[vfx][build] fix API Makefile to descent properly to 'vfx/' dir.

OpenISS/OpenISS,OpenISS/OpenISS,OpenISS/OpenISS,OpenISS/OpenISS,OpenISS/OpenISS,OpenISS/OpenISS,OpenISS/OpenISS