Xcodegen: Add an option 'Run script only when installing'

[ImLaufderZeit]

I often use auto-increment build number script and some scripts that should invoked only when archiving.

_Examples:_
http://crunchybagel.com/auto-incrementing-build-numbers-in-xcode/
https://gist.github.com/sekati/3172554
https://github.com/realm/realm-cocoa/blob/master/scripts/strip-frameworks.sh

Those kind of scripts should run only when archiving (well, just personally I guess so). So I believe 'Run script only when installing' option would be nice...

[yonaskolb]

This requires support from xcodeproj

[yonaskolb]

Fixed in xcodeproj https://github.com/carambalabs/xcodeproj/pull/49

[yonaskolb]

Resolved with workaround in the meantime. Will be in the next release soon

[pepibumur]

We'll have a release tonight so that you can use it @yonaskolb

[yonaskolb]

@ImLaufderZeit This is now in 0.4.0