Lock objc_missing_fld to one thread.

Summary: This fixes a flaky test where some issues would disappear and re-appear.

Reviewed By: da319

Differential Revision: D9027686

fbshipit-source-id: 5ac314096

infer/tests/build_systems/objc_missing_fld/Makefile

@@ -11,7 +11,7 @@ ANALYZER = checkers
 SOURCES = $(CODETOANALYZE_DIR)/A.m $(CODETOANALYZE_DIR)/B.m
 OBJECTS = $(CODETOANALYZE_DIR)/A.o $(CODETOANALYZE_DIR)/B.o
 CLANG_OPTIONS = -c $(OBJC_CLANG_OPTIONS)
-INFER_OPTIONS = --biabduction-only --report-custom-error --developer-mode --project-root $(TESTS_DIR)
+INFER_OPTIONS = -j 1 --biabduction-only --report-custom-error --developer-mode --project-root $(TESTS_DIR)
 INFERPRINT_OPTIONS = --project-root $(TESTS_DIR) --issues-tests
 
 include $(TESTS_DIR)/infer.make