I'm putting this here in case anyone else is suffering through edit-save-compile loops measured in minutes.
https://github.com/seanmonstar/warp/issues/507#issuecomment-605541796
https://github.com/rust-lang/rust/issues/39915#issuecomment-538049306
Changing over to the new lld linker sped up compilation by several orders of magnitude. Life is happy again!