AUTOUIC losing track of include paths
This comes out of the sayonara (a music player, http://www.sayonara-player.com/) package, which no longer builds with CMake 3.9. The "offending" commit is 1cdf7c1b , after which the build fails with
Generating MOC source EWIEGA46WW/moc_GUI_AlternativeCovers.cpp
AutoUic: Error: "/tmp/sayonara/work/sayonara-player/src/GUI/Covers/GUI_AlternativeCovers.h"
Could not find "GUI/Covers/GUI_AlternativeCovers.ui"
It fails similarly when using ninja instead of make. I don't have a minimal example yet, because the sayonara CMakeLists are a steaming pile of WTF -- which might actually be the underlying problem, but then it has changed from "used to work accidentally" to "doesn't work."