The previous logic would cause any non-sorted physical devices to be missed
when aggregating the final list. This caused crashes due to the phys_dev
value not being initialized. The fix is to make sure both sorted and non
sorted physical devices are included in the final output of
setup_loader_term_phys_devs().
The loader ICD ordering could be random on Linux based on using readdir
to find ICD manifest files. This can result in random behaviors as
applications that select only the first device can switch which device is
used. To resolve this, we now sort based on device type and then
internally to the types based on PCI bus information.
This also introduces a VK_LOADER_DEFAULT_DEVICE environment variable
that can be used to force a specific PCI device. This environment variable
is actually a duplicate of the MESA_VK_DEVICE_SELECT variable, which is
also looked for if the loader environment variable is not found.
Note, that at least one ICD must support it for the extension to be used at all.
So we only do the sorting if one ICD supports it.
Fixes part of #657
andrew0229