Compiling ports in a post-9.0-RELEASE world

[Klaus T. Aehlig]

Hi,

> I think some option like "CLANG_SAFE" or "USE_CLANG" (just 
> saying, perhaps a better name can be found) should be added [...]

I also think that it would be very useful to go the same route
as with MAKE_JOBS, i.e., ports can opt in, and in the long run opt out,
of being build with clang. In my opinion, that should also include a 
variable like FORCE_MAKE_JOBS, say FORCE_CLANG, that makes all undecided 
ports (i.e., those neither CLANG_SAFE nor CLANG_UNSAFE) chose clang.

Best,
Klaus