THRIFT-4717: fix up make clean with autoconf
diff --git a/tutorial/dart/Makefile.am b/tutorial/dart/Makefile.am
index 0495aca..0b93ac8 100644
--- a/tutorial/dart/Makefile.am
+++ b/tutorial/dart/Makefile.am
@@ -25,11 +25,19 @@
 all-local: gen-dart/tutorial/lib/tutorial.dart pub-get
 
 clean-local:
-	$(RM) -r gen-*
+	$(RM) -r gen-*/
+	find . -type d -name ".dart_tool" | xargs $(RM) -r
 	find . -type d -name "packages" | xargs $(RM) -r
 	find . -type f -name ".packages" | xargs $(RM)
 	find . -type f -name "pubspec.lock" | xargs $(RM)
 
+dist-hook:
+	$(RM) -r $(distdir)/gen-*/
+	find $(distdir) -type d -name ".dart_tool" | xargs $(RM) -r
+	find $(distdir) -type d -name "packages" | xargs $(RM) -r
+	find $(distdir) -type f -name ".packages" | xargs $(RM)
+	find $(distdir) -type f -name "pubspec.lock" | xargs $(RM)
+
 pub-get: pub-get-gen pub-get-client pub-get-console-client pub-get-server
 
 pub-get-gen: pub-get-tutorial pub-get-shared