Auto merge of #126934 - onur-ozkan:broken-build-cache, r=Kobzol

fix broken build cache caused by rustdoc builds

Currently rustdoc breaks the build cache (due to having different rustflags) when building rustdoc before building another tool (e.g., `x test miri && x test rustdoc && x test miri`).

This change fixes that by moving `on-broken-pipe` into `prepare_cargo_tool` so it is set for all tools.

cc `@RalfJung`

Fixes #123177

Author: bors