Post #2008846

@april i already have partial handling of this in libreboot, because at one point i was build-testing libreboot on debian sid and the proper gcc version wasn't available at gcc in PATH. but i had e.g. gcc-15, and then gnat-13 and gnat-14. and gcc-13. and i had to make lbmk match them up in terms of version. i can just extend that logic to the entire system toolchain, for each component e.g. autoconf, autogen, and other tools. some tools are unversioned. e.g. iasl is just iasl, in openbsd.