As for the patching approach:
you could `git clone url/to/nim/github -b version-2-2` and then `git apply
yourPatch.diff` before calling `build_all.sh` or `build_all.bat`
That way you can bootstrap the compiler with your patch _(i did this for
bootstrapping with zigcc and it works well)_

Another option is to override the path to stdlib to some folder where you have
your patched files
I know the switch to do this exists, but I can't remember the exact name. But if
you search for it in the `nimc` manual it should be there