Qt: unable to find types.h

At several places in the code types.h is included as

" #include sys/types.h "

When I try to do a build, Qt reports that types.h can not be found.

I can locate several versions og types.h, and tried to put one og these directly into the include folder, and changed the include statements to "#include types.h".
This seemed to solve the problem, but og course it is not a viable solution.

I guess that problem is somehow related to environment setup, but I have no idea where to look.

Platform is Windows 10, 64 bit, with Qt 5.9.3, MinGw 5 3.0 and Cmake 3.10.1.