BTW, I'd suggest using `?=' everywhere. It leaves the chance to override value from environ(7) without touching make.conf.
As for port's gcc there are few pitfalls but libmap.conf addresses only runtime linking problem completely avoiding build linking one (rtld vs. ld). BTW, using CPUTYPE?=native should work for any GCC (newer than gcc3*) and clang. If you're after more portable binaries then you'd want to use -mtune=generic but there is no make(1) macro for it.
As for port's gcc there are few pitfalls but libmap.conf addresses only runtime linking problem completely avoiding build linking one (rtld vs. ld). BTW, using CPUTYPE?=native should work for any GCC (newer than gcc3*) and clang. If you're after more portable binaries then you'd want to use -mtune=generic but there is no make(1) macro for it.