THRIFT-2946 Enhance usability of cross test framework

introduce *make fail* to update known failures
diff --git a/Makefile.am b/Makefile.am
index 65dfe9d..5b60c5f 100755
--- a/Makefile.am
+++ b/Makefile.am
@@ -44,7 +44,11 @@
 
 # TODO: generate --server and --client switches from "--with(out)-..." build flags
 cross: precross
-	python test/test.py -s
+	$(PYTHON) test/test.py -s
+
+fail: precross
+	$(PYTHON) test/test.py
+	$(PYTHON) test/test.py --update-expected-failures=overwrite
 
 codespell_skip_files = \
 	*.jar \