fix make -C infer/annotations clean clean

Summary:
also adds these directories and files to .gitignore

.gitignore

@@ -89,4 +89,7 @@ buck-out/
 /infer/src/clang/clang_ast_visit.ml
 /infer/src/clang/clang_ast_main.ml
 
+/infer/annotations/annot_classes/
 /infer/annotations/annotations.jar
+/infer/annotations/processor_classes/
+/infer/annotations/processor.jar

infer/annotations/Makefile

@@ -18,7 +18,7 @@ processor:
 	cd $(PROCESSOR_CLASSES) && cp -r ../resources/META-INF . && jar cvMf processor.jar com META-INF && cp processor.jar ../
 
 clean:
-	rm -r $(ANNOT_CLASSES)
-	rm annotations.jar
-	rm -r $(PROCESSOR_CLASSES)
-	rm processor.jar
+	rm -rf $(ANNOT_CLASSES)
+	rm -f annotations.jar
+	rm -rf $(PROCESSOR_CLASSES)
+	rm -f processor.jar