Bug 1617369 - Reformat recent rust changes with rustfmt r=arai

# ignore-this-changeset

Differential Revision: https://phabricator.services.mozilla.com/D79149

js/src/frontend/smoosh/build.rs

@@ -16,7 +16,9 @@ fn compare(name: &str, orig: &str, copied: &str) {
 
 fn main() {
     match std::env::var("JS_SMOOSH_DISABLE_OPCODE_CHECK") {
-        Ok(_) => { return; },
+        Ok(_) => {
+            return;
+        }
         Err(_) => {}
     };