QBS uses bad target when using Clang on Windows

I'm trying to compile a QBS project using the new Clang6 compiler with MSVC2017 header/lib support on Windows. I verified that the compiler itself works perfectly, i.e. I can compile, link and run basic C++ hello world applications using stdc++ libs from MSVC2017 if the include and lib paths are set correctly.

Compiling with QBS fails however, since QBS keeps adding a bad target x86_64-unknown-unknown-unknown parameter to the compile commands for some reason:

"C:\Program Files\LLVM\bin\clang++.exe" -g -O0 -Wall -Wextra -target x86_64-unknown-unknown-unknown -pipe -fexceptions ......

Compilation works if target is either x86_64-pc-windows-msvc or by simply not setting target and using the compiler default.

The QBS Profile for Clang was added by using qbs setup-toolchains <llvm-path> clang+.exe. Alternatively (and originally) I used QtCreator, added Clang as a new C+ compiler, chose ABI x86-windows-msvc2017-pe-64bit and set it as the Compiler in a new Qt Kit. In both set ups QBS ends up adding x86_64-unknown-unknown-unknown.

Correcting the target using cflags doesn't work either because some qbs internal script detects and explicitly prevents this crude attempt of changing "target".