zig fmt warmup

[marler8997]

It takes about 15 seconds to run zig fmt for the first time after a clean zig installation and it's annoying to have that hang my editor. I think it would be nice if after zigup installs a new version of zig it runs zig fmt --help once to pre-compile it by default. There should also be an option to disable this (--no-fmt-warmup or something).