Revert "Revert "Invalidate @xcode_version only when we set app.xcode_version, and only call unscape_path once""
Revert "Revert "Invalidate @xcode_version only when we set app.xcode_version, and only call unscape_path once""

This reverts commit 6255443a180346d6a3273f75bc8969ff7de3a52c.

hboon/RubyMotion,katsuyoshi/RubyMotion,katsuyoshi/RubyMotion,hboon/RubyMotion,katsuyoshi/RubyMotion,HipByte/RubyMotion,HipByte/RubyMotion,hboon/RubyMotion,katsuyoshi/RubyMotion,HipByte/RubyMotion