mocs_compilation.cpp does not use ConfigSuffix (mocs_compilation_$<CONFIG>.cpp)
An earlier change seems to got lost later on (it's not on master anymore): The change affects the naming of the mocs_compilation.cpp, which should be mocs_compilation_$<CONFIG>.cpp.
For multi-configuration tools like MSVC this is essential, otherwise mocs_compilation.cpp gets changed and compiled every time you switch between configurations.
This change introduced it, but its not in the master anymore:
cmQtAutoGenerators::Init
method: d7e1b93f
// Mocs compilation file
this->MocCompFileRel = "mocs_compilation";
this->MocCompFileRel += this->ConfigSuffix;
this->MocCompFileRel += ".cpp";
Edited by Jahn F.