mission-center: add GPU drivers to LD_LIBRARY_PATH

This fixes an issue where NVIDIA cards will not show up on NixOS.

Under the hood, missioncenter-magpie executable uses nvtop to read
information for and stats about GPU devices. nvtop uses `dlopen` to
load vendor-specific libraries at runtime. For NVIDIA cards, this
requires having the appropriate version of `libnvidia-ml.so` available
under the LD_LIBRARY_PATH or RUNPATH.

Ideally, we would use `addDriverRunpath` directly to edit the
`missioncenter-magpie` RUNPATH. We instead have to wrap it with an
updated LD_LIBRARY_PATH to include the path which `addDriverRunpath`
would have added, as `$out/bin/missioncenter-magpie` is actually an
executable wrapper created by the `wrapGAppsHook4` hook.

pkgs/by-name/mi/mission-center/package.nix

@@ -39,6 +39,7 @@
   wayland,
 
   # magpie wrapper
+  addDriverRunpath,
   libGL,
   vulkan-loader,
 
@@ -128,6 +129,7 @@ stdenv.mkDerivation (finalAttrs: {
   };
 
   nativeBuildInputs = [
+    addDriverRunpath
     blueprint-compiler
     cargo
     libxml2
@@ -178,6 +180,10 @@ stdenv.mkDerivation (finalAttrs: {
           libGL
           libdrm
           vulkan-loader
+
+          # NVIDIA support requires linking libnvidia-ml.so at runtime:
+          # https://github.com/Syllo/nvtop/blob/3.2.0/src/extract_gpuinfo_nvidia.c#L274-L276
+          addDriverRunpath.driverLink
         ]
       }"
   '';