don't pass -C to nm

the nm in our macOS bots don't support that flag and it's not really required

Author: Jorge Aparicio

src/test/run-make/used/Makefile

@@ -7,5 +7,5 @@ all:
 else
 all:
 	$(RUSTC) -C opt-level=3 --emit=obj used.rs
-	nm -C $(TMPDIR)/used.o | grep FOO
+	nm $(TMPDIR)/used.o | grep FOO
 endif