Figure out a way to support and pass through configs #674
Description
llvm toolchains have powerful config file support.
many of the llvm toolchain builds have support for those (todo check which, or add one if there isn't one).
it would be very useful for integration with hardening build flags to support passing through and using the user or project provided llvm toolchain config flags.
this is specifically to better support "distro toolchain" configs, without needing to use the system built llvm toolchain; but instead enable one to pass through opinionated llvm toolchain configs.
This issue is vague for now, but will experiment with a few options to refine this ask more.