pv-runtime: Clarify that we are intentionally hiding Vulkan layers
Mounting a tmpfs to "hide" vulkan/implicit_layer.d is necessary to stop $XDG_DATA_HOME/vulkan/implicit_layer.d from being loaded in preference to /overrides/share/vulkan/implicit_layer.d. However, this is not necessarily obvious to pressure-vessel users attempting to work around an issue like ValveSoftware/steam-runtime#511. Emit a log message that makes it clearer that this is intentional.
Edited by Simon McVittie