[iOS Ext] Fix startup crashes by reverting to previous behaviour.

Watch extensions don't use this code at all.

This reverts commit 9d14fe1000d23e55589eb621100863d204ce24d5.
[iOS Ext] Always pass on the full env to the target.
[iOS Ext] Don't use private API, try to replicate Xcode closely.

Fixes http://hipbyte.myjetbrains.com/youtrack/issue/RM-577.
3.1