Provide newer GNU Config for packages built with autoconf

[Ericson2314]

Autoconf-based packages will need an updated GNU Config to be built. I submitted a patch to GNU config, accepted in http://git.savannah.gnu.org/cgit/config.git/commit/?id=a8d79c3130da83c7cacd6fee31b9acc53799c406, while working on NixOS/nixpkgs#56555. Perhaps the SDK should incorperate this somehow?

[sunfishcode]

I submitted #24 to implement this.