This resolved mutlithreading issues as seen in the `multithreading` test
of the OpenXR CTS.
This patch fixes the test on Vulkan Android and resolves Vulkan
validation errors when running on Linux with OpenGL.
If one of the supplied optional extensions is VK_GOOGLE_display_timing and it is
supported by the driver, vk_bundle::has_GOOGLE_display_timing will be set to true.
This adds some Android support in composition clients,
and fixes the breakage from 2 commits ago.
Thanks to Jakob for finding my error in an earlier version.
As before, on the service side the GPU index the compositor runs on can be selected with
* XRT_COMPOSITOR_FORCE_GPU_INDEX=INDEX1
By default xrGetVulkanGraphicsDevice() will suggest the same GPU the compositor runs on.
It is also possible to override the GPU index suggested to applications with
* XRT_COMPOSITOR_FORCE_CLIENT_GPU_INDEX=INDEX2
The reason this is both done on the service side is that if compositor and client run
on different GPUs, the swapchains use linear tiling instead of optimal tiling.
To make chosen GPUs comparable across the compositor's and the client's vulkan instance,
VkPhysicalDeviceIDProperties.deviceUUID is used.
Instead of maintaining this chunk of code and build options, the Vulkan
loader can be used to load up validation. This has the advantage that no
layer name needs to be hard coded inside Monado, which was subject of
change recently.
Instead of using our own environment variable we can easily set the one
from the loader, e.g. `VK_INSTANCE_LAYERS=VK_LAYER_KHRONOS_validation`.
