Fix uploading ipa to iTunes connect from subdirectory

If you use the `-f` command line option and point it to a relative or absolute path, it fails to copy the ipa.

E.g.:

```
ipa distribute:itunesconnect -u -a 'john@doe.com' -i 123456 -f /Users/Jenkins/workspace/job/build/release/App-release-1.2.3-45678-db1deb3-master.ipa
```