Rollup merge of rust-lang#125715 - lqd:rmake-cleanup, r=jieyouxu

remove unneeded extern crate in rmake test

Cleanup requested in rust-lang#125493 (comment)

r? jieyouxu
`@bors` rollup=always

Author: matthiaskrgr

Diff for: tests/run-make/rust-lld-by-default/rmake.rs

@@ -4,8 +4,6 @@
 //@ needs-rust-lld
 //@ only-x86_64-unknown-linux-gnu
 
-extern crate run_make_support;
-
 use run_make_support::regex::Regex;
 use run_make_support::rustc;
 use std::process::Output;