Compile static Mutex where possible

A few of Rustup's `lazy_static!` instances are for simple locks.
These are easy to evaluate at compile time, and doing so is stable,
so reduce usage of the more heavyweight dependency.

Author: workingjubilee

download/tests/read-proxy-env.rs

@@ -9,13 +9,10 @@ use std::thread;
 use std::time::Duration;
 
 use env_proxy::for_url;
-use lazy_static::lazy_static;
 use reqwest::{blocking::Client, Proxy};
 use url::Url;
 
-lazy_static! {
-    static ref SERIALISE_TESTS: Mutex<()> = Mutex::new(());
-}
+static SERIALISE_TESTS: Mutex<()> = Mutex::new(());
 
 fn scrub_env() {
     remove_var("http_proxy");

src/cli/self_update/test.rs

@@ -2,7 +2,6 @@
 
 use std::sync::Mutex;
 
-use lazy_static::lazy_static;
 #[cfg(not(unix))]
 use winreg::{
     enums::{HKEY_CURRENT_USER, KEY_READ, KEY_WRITE},
@@ -38,9 +37,7 @@ fn restore_path(p: Option<RegValue>) {
 /// Support testing of code that mutates global path state
 pub fn with_saved_path(f: &mut dyn FnMut()) {
     // Lock protects concurrent mutation of registry
-    lazy_static! {
-        static ref LOCK: Mutex<()> = Mutex::new(());
-    }
+    static LOCK: Mutex<()> = Mutex::new(());
     let _g = LOCK.lock();
 
     // On windows these tests mess with the user's PATH. Save