[driver] handle removal of symlinks in infer-out
[driver] handle removal of symlinks in infer-out

Summary:
This would fail before and works as expected now:

```
$ infer -- clang -c hello.c
$ cd infer-out/ && ln -s ../foo && cd ..
$ infer -- clang -c hello.c # crashes because it fails to delete infer-out/foo
```

Reviewed By: jberdine

Differential Revision: D4398763

fbshipit-source-id: 38465f8

ryoon/infer,facebook/infer,ropas/infer,ryoon/infer,facebook/infer,ryoon/infer,blzq/infer,facebook/infer,jvillard/infer,jvillard/infer,facebook/infer,jsachs/infer,blzq/infer,facebook/infer,jvillard/infer,jvillard/infer,jvillard/infer,ropas/infer,blzq/infer,blzq/infer,jsachs/infer,ropas/infer,blzq/infer,jsachs/infer,ropas/infer,blzq/infer,ryoon/infer,jsachs/infer,ryoon/infer,ryoon/infer,ropas/infer,ropas/infer,jvillard/infer,jsachs/infer,jvillard/infer,facebook/infer,facebook/infer,jsachs/infer