Good new progress on musl-cross-make today (splitting binutils & gcc build trees so they don't have to be matching versions).https://github.com/richfelker/musl-cross-make/commit/defdbb450577b32399b780a94ebbdf2221e23583 …
As part of next big overhaul/refactor I've also worked out the basics for cowpatch, my utility that will let you apply a diff to a symlink-to-dir, breaking down real dirs/files only minimally as needed to apply the patch.