we need to move away from the magic-ABI-env-vars that gcc-config uses to hook
in flags transparently. as such, i'm changing multilib.eclass'
multilib_toolchain_setup so that it sets each toolchain component explicitly:
export CC="$(tc-getCC) $(get_abi_CFLAGS)"
seems to work on the few packages that actually do ABI-changes inside of the
ebuild, but in case people's multilib packages break, this should be an easy
thing to check.