For testing. This reduces memory needed for JIT test. The -f flag will print 
the full patch of failures (want to keep this). 

--- mozilla-esr31/js/src/Makefile.in.orig	2015-06-04 17:42:51.305891808 -0700
+++ mozilla-esr31/js/src/Makefile.in	2015-06-04 17:42:51.308235809 -0700
@@ -152,7 +152,7 @@
 
 check-jit-test::
 	$(JITTEST_ASAN_ENV) $(wildcard $(RUN_TEST_PROGRAM)) $(PYTHON) -u $(srcdir)/jit-test/jit_test.py \
-	        --no-slow --no-progress --tinderbox --tbpl $(JITTEST_VALGRIND_FLAG) \
+	        --no-slow --no-progress --tinderbox --tbpl -j 2 -f $(JITTEST_VALGRIND_FLAG) \
 	        $(DIST)/bin/$(JS_SHELL_NAME)$(BIN_SUFFIX)
 
 check:: check-style