Fix resolution-err.ll

chmod tries to be very helpful on some platforms and prevent naive mistakes, by warning the user. This results in the following error during the test:

```chmod: ...resolution-err.ll.tmp.resolution.txt: new permissions are r--rw-rw-, not r--r--r--```

To fix the test, call chmod with u.

Differential Revision: https://reviews.llvm.org/D100417