The rustfmt configuration is linked to the default from
build/soong/scripts. This is similar to how clang-format is setup for
system/core.
Test: Added a commit with a bogus lib.rs and run repo upload.
An error is returned by the rusfmt hook.
Bug: 157146658
Change-Id: If346bdd73c9cdd84c3cd98ed00b95ed9d790aa4f
