> The package's Makefile includes bsd.prefs.mk with
> .include "../../mk/bsd.prefs.mk"
> and then adds to CFLAGS with
> CFLAGS+=

this means that every package manipulating CFLAGS or some similar
variable must include ../../mk/bsd.prefs.mk in its Makefile? (my impression
so far is that Makefiles do so only when querying some variable defined
therein).

> 
> The scenario you describe would occur if the package
> set CFLAGS _before_ importing bsd.prefs.mk.

yes

> Especially since CFLAGS in mk.conf is usually set
> with "=", not "+=".

that was my initial point, that one runs into conflict when doing so.

-- 
Georg Schwarz    http://home.pages.de/~schwarz/
 georg.schwarz@freenet.de  +49 178 8545053