If filemon is used then there is no need to generate dependency files during
compilation as the .meta files will achieve the same result.
This is a temporary solution until FAST_DEPEND is default. Once that is
default there will be an option to disable dependency generation entirely
as it is only useful if an incremental build is planned, thus META_MODE+filemon
can enable that option to short-circuit all FAST_DEPEND-related logic.
Sponsored by: EMC / Isilon Storage Division