Auto merge of #111566 - clubby789:bootstrap-override-config, r=ozkanonur

Override config.toml options from command line

https://rust-lang.zulipchat.com/#narrow/stream/326414-t-infra.2Fbootstrap/topic/Running.20tests.20on.20precompiled.20rustc/near/357763280

cc `@jyn514`

Author: bors