pv-runtime: Don't append layers to VK_DRIVER_FILES under FEX-Emu
Layers are not drivers, and their search path is different.
Fixes: 451544d8 "Add support for FEX-Emu graphics thunking"
Noticed while looking at steamrt/tasks#239.
Layers are not drivers, and their search path is different.
Fixes: 451544d8 "Add support for FEX-Emu graphics thunking"
Noticed while looking at steamrt/tasks#239.