Fix some issues that seem to have appeared in the CMake configuration.

Fixes this issue:
> 2>  Generating ../moc_.cxx
> 2>  moc: openmw/components: No such file
> 2>C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\Microsoft.CppCommon.targets(151,5): error MSB6006: "cmd.exe" exited with code 1.

As well as actually allowing installer package creation on windows.