pressure-vessel: Look for internal Nvidia helper libraries by name
The Nvidia drivers have various helper libraries that get loaded as
dependencies. Some of them are hard dependencies via DT_NEEDED, but
others are loaded dynamically with dlopen(): for example,
at the time of writing, libGLX_nvidia.so.0 has a DT_NEEDED
dependency on libnvidia-glcore.so.VERSION which is sufficient for
OpenGL, but dlopens libnvidia-glvkspirv.so.VERSION when asked to act
as a Vulkan driver.
Normally, we can find these libraries by their entry in
soname_globs_even_if_older[], by using the soname-match: syntax
to search /etc/ld.so.cache for SONAMEs matching a glob pattern like
libnvidia-glvkspirv.so.*. This works because OS distributions normally
install these libraries into the default system library directory
/usr/lib{,32,64} or /usr/lib/MULTIARCH, which is indexed by
ldconfig(8).
However, when using Canonical's Snap apps, the Nvidia drivers can only
be found in the LD_LIBRARY_PATH, and soname-match: does not
implement LD_LIBRARY_PATH search. This leads to a situation similar
to https://github.com/ValveSoftware/steam-runtime/issues/632 where
these libraries are not found. The result is that the Nvidia Vulkan
driver is present, but fails to load.
If we can read /sys/module/nvidia/version (which Flatpak also relies
on as its way to discover the current Nvidia driver version), then we
can resolve this by looking for each of the known libraries by name.
This takes into account LD_LIBRARY_PATH and DT_RUNPATH, not just
the ld.so.cache. Making this effective will require a snapd change,
to make /sys/module/nvidia/version readable.
Helps: https://github.com/ValveSoftware/steam-runtime/issues/586