Rollup merge of #58704 - taiki-e:extern-crate, r=Centril

Remove some unnecessary 'extern crate'

cc #58099

r? @Centril

src/bootstrap/bin/main.rs

@@ -7,8 +7,6 @@
 
 #![deny(warnings)]
 
-extern crate bootstrap;
-
 use std::env;
 
 use bootstrap::{Config, Build};

src/bootstrap/bin/rustc.rs

@@ -17,8 +17,6 @@
 
 #![deny(warnings)]
 
-extern crate bootstrap;
-
 use std::env;
 use std::ffi::OsString;
 use std::io;

src/bootstrap/bin/rustdoc.rs

@@ -4,8 +4,6 @@
 
 #![deny(warnings)]
 
-extern crate bootstrap;
-
 use std::env;
 use std::process::Command;
 use std::path::PathBuf;

src/bootstrap/bin/sccache-plus-cl.rs

@@ -1,5 +1,3 @@
-extern crate cc;
-
 use std::env;
 use std::process::{self, Command};
 

src/bootstrap/lib.rs

@@ -114,23 +114,11 @@ extern crate build_helper;
 extern crate serde_derive;
 #[macro_use]
 extern crate lazy_static;
-extern crate serde_json;
-extern crate cmake;
-extern crate filetime;
-extern crate cc;
-extern crate getopts;
-extern crate num_cpus;
-extern crate toml;
-extern crate time;
-extern crate petgraph;
 
 #[cfg(test)]
 #[macro_use]
 extern crate pretty_assertions;
 
-#[cfg(unix)]
-extern crate libc;
-
 use std::cell::{RefCell, Cell};
 use std::collections::{HashSet, HashMap};
 use std::env;

src/liballoc/benches/lib.rs

@@ -1,8 +1,6 @@
 #![feature(repr_simd)]
 #![feature(test)]
 
-extern crate rand;
-extern crate rand_xorshift;
 extern crate test;
 
 mod btree;

src/liballoc/tests/lib.rs

@@ -8,9 +8,6 @@
 #![feature(unboxed_closures)]
 #![feature(vecdeque_rotate)]
 
-extern crate core;
-extern crate rand;
-
 use std::hash::{Hash, Hasher};
 use std::collections::hash_map::DefaultHasher;