CMake files doesn't ensure same wchar_t size as Qt was built with

When using e.g. QString::fromWCharArray (or one of the related ones) build fails in at least debug mode because the size of wchar_t is different in the default cmake configuration than what Qt is built with by default.

I would have expected the cmake bits to set that up for me automatically.

Compiler errors are reported like this:
karchivetest.cpp.obj : error LNK2001: unresolved external symbol "__declspec(dll
import) public: static class QString __cdecl QString::fromWCharArray(unsigned sh
ort const *,int)" (_imp?fromWCharArray@QString@@SA?AV1@PBGH@Z)
karchivetest.exe : fatal error LNK1120: 1 unresolved externals
LINK Pass 1 failed. with 1120

It is apparantly a command line switch to msvc what size a wchar_t is.