Appveyor: Init git submodules before build
Appveyor: Init git submodules before build

SaschaWillems/Vulkan,jpbruyere/Vulkan,grim210/Vulkan,SaschaWillems/Vulkan,SaschaWillems/Vulkan,grim210/Vulkan,SaschaWillems/Vulkan,jpbruyere/Vulkan,SaschaWillems/Vulkan