Slightly alter the handling of LOCAL_LIB_DIRS to skip addition of
directories in LOCAL_LIB_DIRS if they are subdirectories of directories
listed in LOCAL_DIRS.  This allows a hierarchy like:

	foo
	foo/lib
	foo/usr.bin
	foo/usr.sbin

to be supported with LOCAL_DIRS=foo LOCAL_DIRS=foo/lib.

MFC after:	1 week
Sponsored by:	DARPA, AFRL