Stephen Kelly authored Sep 26, 2015 and Brad King committed Sep 29, 2015

The Ninja generator and Visual Studio generators are special-cased for the
QtAutogen feature.  In order to reduce the number of custom targets, the Visual
Studio generators prefer to create custom commands instead, and in order to
create appropriate Ninja files, generated rcc files are listed as byproducts.

This requires the use of the GetConfigCommonSourceFiles API of the
cmGeneratorTarget for those generators when initializing the autogen target.
The initializer method is called from Compute() after the cmGeneratorTarget
objects are created, however the initialization of the object directory occurs
later in the InitGeneratorTargets method.  That means that the resulting object
locations are computed incorrectly and cached before the object directory is
determined, so the generated buildsystem can not find the object files.

The initialization of the object directory was split from the creation of
cmGeneratorTarget instances in com...