set `on-broken-pipe` in `prepare_cargo_tool`

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.

Signed-off-by: onur-ozkan <work@onurozkan.dev>