Don't print "command failed" unless the build is verbose

The full command isn't very helpful to the user; it still needs
additional environment variables to be run, and it usually doesn't offer
much more info about what went wrong. Hide it behind `--verbose`.

Author: jyn514

src/bootstrap/compile.rs

@@ -1359,11 +1359,11 @@ pub fn stream_cargo(
     // Make sure Cargo actually succeeded after we read all of its stdout.
     let status = t!(child.wait());
     if !status.success() {
-        eprintln!(
+        builder.build.verbose(&format!(
             "command did not execute successfully: {:?}\n\
                   expected success, got: {}",
             cargo, status
-        );
+        ));
     }
     status.success()
 }