Creator: Trouble setting up kit with VS2015 compiler

[Asperamanca]

I have Qt Creator 4.5.1 and a working Qt 4.8.7 running on Visual Studio 2015 (Working means: I can open Visual Studio 2015, and can compile and debug projects 32bit projects using that Qt 4.8.7 version).

The VS2015 compiler is auto detected by Creator. Now I try to add a manual kit:

• Device Type: Desktop
• Device: Local PC
• Sysroot: <empty>
• C Compiler: Microsoft Visual C++ Compiler 14.0 (x86)
• C++ Compiler: Microsoft Visual C++ Compiler 14.0 (x86)
• Environment: No changes apply
• Debugger: None
• Qt version: 4.8.7 (=the same version I set in my Visual Studio project settings)
• Qt mkspec: <empty>

Kit shows me a warning (no debugger), but that's fine.

But as soon as I change the active kit of a project to this VS2015 kit, my clang code model goes crazy:

vcruntime.h:229:22: error: 'short wchar_t' is invalid

**<part of include stack removed here for readability>**

QSharedPointer:1:10: note: in file included from C:\Qt\4.8.7\include\QtCore\QSharedPointer:1:
qsharedpointer.h:1:10: note: in file included from C:\Qt\4.8.7\include\QtCore\qsharedpointer.h:1:
qsharedpointer.h:50:11: note: in file included from C:\Qt\4.8.7\include\QtCore\..\..\src\corelib\tools\qsharedpointer.h:50:
...
xlocale:9:10: note: in file included from C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\xlocale:9:
typeinfo:29:10: note: in file included from C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\typeinfo:29:
vcruntime_typeinfo.h:10:10: note: in file included from C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\vcruntime_typeinfo.h:10:

So far, I have experimented with

*msvc* {
    QMAKE_CXXFLAGS += /Zc:wchar_t-
}

in my .pro-file (and also the opposite /Zc:wchar_t), but it does not seem to have any effect.

Any suggestion what I have done wrong / what I can do?