[infer] Fix `make clean` of ObjC frontend test

Summary:
The `make clean` did not remove objects and dot files, so

```
infer/tests/codetoanalyze/objc/frontend$ make test
infer/tests/codetoanalyze/objc/frontend$ make clean
infer/tests/codetoanalyze/objc/frontend$ make test
```

the second `make test` did nothing.  This diff adds additional regular
expressions to clean all objects and dot files generated.

Reviewed By: ngorogiannis

Differential Revision: D24566169

fbshipit-source-id: b8c50c922

infer/tests/codetoanalyze/objc/frontend/arc/Makefile

@@ -23,3 +23,5 @@ SOURCES = \
 
 include $(TESTS_DIR)/clang-frontend.make
 include $(TESTS_DIR)/objc.make
+
+CLEAN_EXTRA += *.o ../*/*.test.dot ../*/*/*.test.dot

infer/tests/codetoanalyze/objc/frontend/noarc/Makefile

@@ -61,3 +61,5 @@ SOURCES = \
 
 include $(TESTS_DIR)/clang-frontend.make
 include $(TESTS_DIR)/objc.make
+
+CLEAN_EXTRA += *.o ../*/*.test.dot ../*/*/*.test.dot