Investigate using xcrun to produce the IPA

[lukeredpath]

It looks like I might be able to strip out the custom IPA packaging code and replace it with xcrun.

Need to investigate, but it's always better to use existing tools for the right job.

[victor]

Please look also into using xcodebuild … archive as a way to create an archive, without having to guess at the DerivedData folder location.
Unfortunately, this action is buggy in 4.0.2. Either 4.1 or 4.2 is needed.