IFW: Build with static MSVC runtime

For Qt 5, do patch the "win32-" mkspecs as described in the IFW
documentation. This frees us from having to prepare an already patched
Qt source file.

Change-Id: I72458df720f43c02227d703800e0858abc86e0e6
Reviewed-by: Iikka Eklund <iikka.eklund@theqtcompany.com>