build:  Fix puzzles build due to missing dependency

As rbcompat.h is -include'd on the command line, the mkdep script doesn't
pick it up.  Explicitly add the dependency to lang_enum.h to the makefile.

Also add lang_enum.h to the 'make clean' target!

Change-Id: I33c8ed0cd5c1d44dce02ac9285469c0e4feac00e
2 files changed