c8ded52601
LLVM 11 has been unsupported since 45591408b18e7f93fcf8c09210c9a5a102d84b37, so this doesn't need to be conditional on the LLVM version.
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.