allow setting the provisioning profile (or the target device) when building from the command line for iOS

If one wants to build an application that runs a given device, and has multiple provisioning profiles he might have to select the correct one.
when calling xcodebuild this can be acheived with

xcodebuild PROVISIONING_PROFILE=<uid>

optionally one might want also to specify the signing CODE_SIGN_IDENTITY (see https://developer.apple.com/library/ios/documentation/DeveloperTools/Reference/XcodeBuildSettingRef/1-Build_Setting_Reference/build_setting_ref.html )

A way to pass arbitrary build settings to xcodebuild would be useful (or at least a way to pass in these two).