[rake/iOS] Fail when targeting a sim SDK older than deployment target.
[rake/iOS] Fail when targeting a sim SDK older than deployment target.

jjaffeux/RubyMotion,HipByte/RubyMotion,HipByte/RubyMotion,hboon/RubyMotion,incbee/RubyMotion,katsuyoshi/RubyMotion,incbee/RubyMotion,HipByte/RubyMotion,incbee/RubyMotion,incbee/RubyMotion,katsuyoshi/RubyMotion,jjaffeux/RubyMotion,katsuyoshi/RubyMotion,katsuyoshi/RubyMotion,beni55/RubyMotion,hboon/RubyMotion,jjaffeux/RubyMotion,beni55/RubyMotion,beni55/RubyMotion,jjaffeux/RubyMotion,hboon/RubyMotion,beni55/RubyMotion