configure.build_arch

[Jack Howarth]

   Reading through the commits on the configure.build_arch feature
in port, I am rather surprised that invoking that doesn't also
set the triplets for configure as well as passing the -m32 or
-m64 compiler flags. Wouldn't you at least want to set
--target= to the appropriate value so that configure understood
what architecture it was going to build for? I suppose such a
change might be an option to patching config.guess for those
Portfiles that use configure.build_arch. This would make sure
that configure was given --target=x86_64-apple-darwin9/10
when -m64 (or -arch x86_64?) was passed through the invoking
configure.build_arch.
                   Jack