CMAKE_UNITY_BUILD and CTL/ALT/b generates error

when using CMAKE_UNITY_BUILD QtCreator CTL/ALT/b alwys gives an error, such as:

ninja: error: unknown target 'CMakeFiles/TiledPatternMaker.dir/motifs/tile_motif.cpp.obj'
09:39:13: The process "C:\Qt\Tools\CMake_64\bin\cmake.exe" exited with code 1.
Error while building/deploying project TiledPatternMaker (kit: 6.5.0 static)
When executing step "Build"

Perhaps this is not fixable, so instead if a unity build is set ON in CMake, CTL/ALT/b should be redirected to perform a CTL/b instead of generating an error.  

(I guess you could say 'don't press that button' and you wont get the error, but substituting the action for unity builds makes sense to me)