On Thu, 10 Aug 2000, David Brownlee wrote:
> 	excluding postfix (or anything else) in a build:
> 	    It would be nice to fix this in a generic way - any
> 	    volunteers? One idea would be to have a SUBDIR_EXCLUDE
> 	    variable. If set, bsd.subdir.mk would run through SUBDIR
> 	    and remove anything in SUBDIR_EXCLUDE. You would only pay
> 	    the extra processing cost if SUBDIR_EXCLUDE were set, but
> 	    it would make it easier to produce 'cut down' builds.

FreeBSD's bsd.subdir.mk has an interesting solution to this
problem.  You set up a parallel directory tree in which you
store files that can override SUBDIRS for the source tree.

# SUBDIR_CHANGE A directory-tree that contains overrides for
#               corresponding build subdirs.
#               Each override is a file containing one subdirname per line:
#                  'subdirlist'  is a pure override
#                  'subdirdrop'  drops directories from the build
#                  'subdiradd'   adds directories to the build

--apb (Alan Barrett)