Put the following files from the "Windows Driver Kit version 7.0.0" into the x86 and x64 subfolders to build the WinUSB Add-on installer:

dpinst.exe (from redist\Difx\dpinst\MultiLin)
dll\winusbcoinstaller2.dll (from redist\winusb)
dll\WUDFUpdate_01009.dll (from redist\wdf)
dll\WdfCoInstaller01009.dll (from redist\wdf)