Support for .gyb in source files

[hakkurishian]

  targets:
    MyTarget:
    sources : [Myfile.gyb]

Adding gyb files to the source list does not work using project specs, while it works in Xcode to add them to the copy source files phase. For one project, this prevents me to use the tool, since I am relying on source code generated from sources in a build rule.

Is there any reason not to include gyb files into the source list?