Unrolled build for rust-lang#130900

Rollup merge of rust-lang#130900 - capickett:empty-description-rust-version, r=albertlarsan68

Do not output () on empty description

When passing an explicitly empty description string, as explained here https://github.com/rust-lang/rust/blob/master/config.example.toml#L611-L613, my expectation is that the resulting rustc will be compatible with upstream.

However, it seems that instead, a `()` is added to the end of the version string, causing the version compatibility check to fail. My proposed fix here would be to instead only print `({description})` if `description` is a non-empty string.

Author: rust-timer

Diff for: src/bootstrap/src/lib.rs

@@ -1575,9 +1575,11 @@ Executed at: {executed_at}"#,
     fn rust_version(&self) -> String {
         let mut version = self.rust_info().version(self, &self.version);
         if let Some(ref s) = self.config.description {
-            version.push_str(" (");
-            version.push_str(s);
-            version.push(')');
+            if !s.is_empty() {
+                version.push_str(" (");
+                version.push_str(s);
+                version.push(')');
+            }
         }
         version
     }