- Stop using git to build as it is unmaintainable due to submodules,
but more importantly because src/vendor is no longer bundled. Just
fetch the source already generated that has all dependencies bundled.
It may be a bit slower to get updates but is far more maintainable.
- Copy all patches to lang/rust-nightly/files since they may not always
apply exactly between both versions.
- Add in patch for llvm-config getting -lexecinfo wrong, this is in
review with LLVM at https://reviews.llvm.org/D42702.
- Bring in other random updates from lang/rust.
