[OSX] fix a bug on OSX platform where compiler flags for iOS are passed when it generates bridgesupport file for vendor library

http://hipbyte.myjetbrains.com/youtrack/issue/RM-315
move special configuration for iOS/OSX platform from gen_bridge_metadata()
[rake] Raise error if cleaning does not succeed.

Fixes https://hipbyte.freshdesk.com/helpdesk/tickets/1359.
[spec] Deprecate block to the `tests` method of the view test helpers.
2.15