Rollup merge of #126230 - onur-ozkan:followup-126225, r=Mark-Simulacrum

tidy: skip submodules if not present for non-CI environments

Right now tidy requires rustc-perf to be fetched as it checks its license, but this doesn't make sense for most contributors since rustc-perf is a dist-specific tool and its license will not change frequently, especially during compiler development. This PR makes tidy to skip rustc-perf if it's not fetched and if it's not running in CI.

Applies rust-lang/rust#126225 (comment) and reverts #126225.

Author: matthiaskrgr