223f107b48
Remove references to git.io The git.io service is shutting down soon (see https://github.blog/changelog/2022-04-25-git-io-deprecation/). This removes the references of those short links with the actual destination.
rustc_target contains some very low-level details that are
specific to different compilation targets and so forth.
For more information about how rustc works, see the rustc dev guide.