Currently a developer that starts blender with `--debug-gpu` or
runs the GPU test cases can receive an error when not the full
VulkanSDK is installed.
The VulkanSDK isn't required for normal developement and
therefore it is better to show it as a warning.
NOTE: VulkanSDK is adviced to use when developing in the Vulkan
backend as it contains tools that helps/speed up the development
and validation during development.
Jeroen Bakker