THRIFT-4019: Dart Makefiles should also clean pubspec.lock
Client: Dart
Patch: Mark Erickson <merickson@apache.org>

This closes #1150
diff --git a/test/dart/Makefile.am b/test/dart/Makefile.am
index 6f97de9..e274771 100644
--- a/test/dart/Makefile.am
+++ b/test/dart/Makefile.am
@@ -38,6 +38,7 @@
 	$(RM) -r gen-dart test_client/.pub
 	find . -type d -name "packages" | xargs $(RM) -r
 	find . -type f -name ".packages" | xargs $(RM)
+	find . -type f -name "pubspec.lock" | xargs $(RM)
 
 client: stubs
 	${DART} test_client/bin/main.dart