Build scripts: add support for NMake project generator
Build scripts: add support for NMake project generator

Requires nmake.exe in PATH (try running from Visual Studio Command
Prompt, or use vcvars*.bat).

Change-Id: I2bfcfa46a5529066000745209673804b1863f1fc

chadversary/deqp,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/VK-GL-CTS,chadversary/deqp,chadversary/deqp,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,chadversary/deqp,chadversary/deqp,chadversary/deqp,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS