nixos: Don't set LD_LIBRARY_PATH for graphics drivers that don't need it.

A new internal option `hardware.opengl.setLdLibraryPath` is added which controls if `LD_LIBRARY_PATH` should be set to `/run/opengl-driver(-32)/lib`. It is false by default and is meant to be set to true by any driver which requires it. If this option is false, then `opengl.nix` and `xserver.nix` will not set `LD_LIBRARY_PATH`.

Currently Mesa and NVidia drivers don't set `setLdLibraryPath` because they work with libglvnd and do not override libraries, while `amdgpu-pro`, `ati` and `parallels-guest` set it to true (the former two really need it, the last one doesn't build so is presumed to).

Additionally, the `libPath` attribute within entries of `services.xserver.drivers` is removed. This made `xserver.nix` add the driver path directly to the `LD_LIBRARY_PATH` for the display manager (including X server). Not only is it redundant when the driver is added to `hardware.opengl.package` (assuming that `hardware.opengl.enable` is true), in fact all current drivers except `ati` set it incorrectly to the package path instead of package/lib.

This removal of `LD_LIBRARY_PATH` could break certain packages using CUDA, but only those that themselves load `libcuda` or other NVidia driver libraries using `dlopen` (not if they just use `cudatoolkit`). A few have already been fixed but it is practically impossible to test all because most packages using CUDA are libraries/frameworks without a simple way to test.

Fixes #11434 if only Mesa or NVidia graphics drivers are used.

nixos/modules/hardware/video/amdgpu-pro.nix

@@ -30,10 +30,11 @@ in
     nixpkgs.config.xorg.abiCompat = "1.19";
 
     services.xserver.drivers = singleton
-      { name = "amdgpu"; modules = [ package ]; libPath = [ package ]; };
+      { name = "amdgpu"; modules = [ package ]; };
 
     hardware.opengl.package = package;
     hardware.opengl.package32 = package32;
+    hardware.opengl.setLdLibraryPath = true;
 
     boot.extraModulePackages = [ package ];