[iOS8] fix @executable_path for iOS platform
[iOS8] fix @executable_path for iOS platform

http://hipbyte.myjetbrains.com/youtrack/issue/RM-558

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