local-host tools used during NetBSD xcompilation

Right now, there are a fair amount of host-locale binaries built and run
during the NetBSD build process - e.g. a bunch of bits in games/, 
sys/arch/i386/stand/genprom, etc. Right now, there seem to be no
flags, no defines, or anything other than "cc -O -c -o".

The recent __attribute(foo) -> __foo changes have repeatedly broken
xcompilation a fair bit - but even compiling on a native system, I'm
kinda leery of blindly invoking cc and hoping everything works.

I'd like to see something akin to pkgsrc's buildwrappers to whinge
and complain if the non-USE_TOOLS compiler is used during the build
- but at this point, I'd be happy with the .lo and/or bsd.hostprog.mk
related stuff emit some extra defines. Unfortunately, I have no idea
where all that sort of thing lives in the bowels of mk/ - any of
y'all have insight?