Best way to set gcc.arch for a subset of packages in overlay?

I have some packages that I want to build with gcc.arch = "x86-64-v3" to enable SIMD instructions, but I don’t want to set it globally because then I’d have to rebuild everything.

How can I override this setting for just a couple of packages in an overlay? e.g. I want to set it for the ‘meshoptimizer’, ‘eigen’ and ‘ceres-solver’ packages.