Rustup 1.27.1: Minor Bug Fixes Can Have a Big Positive Impact

The headlines for this release are: Prebuilt Rustup binaries should be working on older macOS versions again. rustup-init will no longer fail when fish is installed, but ~/.config/fish/conf.d hasn't been created. Regressions regarding symlinked RUSTUP_HOME/(toolchains|downloads|tmp) have been addressed.