After different tests and building processes I'm able to build and run an application with WebKit on Windows 10 with MinGW.
I simply replaced original shipped WebKit with a fresh one from git repository.
Working software versions are:
MinGW-w64 5.2.0 i686 posix dwarf
OpenSSL 1.0.2d
zlib 1.2.8
ICU4c 55.1
Qt 5.5.0 (with fresh qtwebkit module from git)
I'm using Windows 10 64bit with both Windows SDK installed and DirectX SDK (installed with DXSDK_Jun10.exe), but I think that it's possible to disable angle and force OpenGL to desktop in order to avoid installing MSVC and DirectX.
I'm trying to compile the same environment on 64bit. I'll update this thread on finish.