[dartdev] show the stack trace when we fail with an unexpected exception

Change-Id: Idf0d39b3887393f8cb8b763fa66e52b2721ce3db
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/148901
Reviewed-by: Jaime Wren <[email protected]>
Commit-Queue: Devon Carew <[email protected]>

Author: devoncarew

pkg/dartdev/bin/dartdev.dart

@@ -13,12 +13,13 @@ main(List<String> args) async {
   try {
     dynamic result = await runner.run(args);
     exit(result is int ? result : 0);
-  } catch (e) {
+  } catch (e, st) {
     if (e is UsageException) {
       stderr.writeln('$e');
       exit(64);
     } else {
       stderr.writeln('$e');
+      stderr.writeln('$st');
       exit(1);
     }
   }