rustc_driver: Omit stage info for stage2+

Author: richo

src/librustc_driver/lib.rs

@@ -487,10 +487,6 @@ pub fn stage_str() -> Option<&'static str> {
         Some("stage0")
     } else if cfg!(stage1) {
         Some("stage1")
-    } else if cfg!(stage2) {
-        Some("stage2")
-    } else if cfg!(stage3) {
-        Some("stage3")
     } else {
         None
     }
@@ -508,7 +504,9 @@ pub fn version(binary: &str, matches: &getopts::Matches) {
         println!("commit-date: {}", unw(commit_date_str()));
         println!("host: {}", config::host_triple());
         println!("release: {}", unw(release_str()));
-        println!("stage: {}", unw(stage_str()));
+        if let Some(stage) = stage_str() {
+            println!("stage: {}", stage);
+        }
     }
 }