The generated headers are found under builddir/mx, which is not in the include path. A patch for both 1.4 and master is [here](https://github.com/Guacamayo/meta-clutter/blob/master/recipes-graphics/mx/mx/fix-test-includes.patch).
The generated headers are found under builddir/mx, which is not in the include path. A patch for both 1.4 and master is here.