treewide: refactor to use libglvnd

* Implement libGL as a symlink package which uses libraries from libglvnd and
  headers from Mesa (since ones from libglvnd are outdated).
* Use libGL_driver.driverLink treewide; add FHS paths where possible.

pkgs/development/libraries/libva/1.0.0.nix

@@ -1,5 +1,5 @@
 { stdenv, lib, fetchurl, libX11, pkgconfig, libXext, libdrm, libXfixes, wayland, libffi
-, mesa_noglu
+, libGL, libGL_driver
 , minimal ? true, libva
 }:
 
@@ -17,11 +17,12 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ pkgconfig ];
 
   buildInputs = [ libdrm ]
-    ++ lib.optionals (!minimal) [ libva libX11 libXext libXfixes wayland libffi mesa_noglu ];
+    ++ lib.optionals (!minimal) [ libva libX11 libXext libXfixes wayland libffi libGL ];
   # TODO: share libs between minimal and !minimal - perhaps just symlink them
 
   configureFlags =
-    [ "--with-drivers-path=${mesa_noglu.driverLink}/lib/dri" ] ++
+    # Add FHS paths for non-NixOS applications.
+    [ "--with-drivers-path=${libGL_driver.driverLink}/lib/dri:/usr/lib/dri:/usr/lib32/dri" ] ++
     lib.optionals (!minimal) [ "--enable-glx" ];
 
   installFlags = [ "dummy_drv_video_ladir=$(out)/lib/dri" ];

pkgs/development/libraries/libva/default.nix

@@ -1,6 +1,6 @@
 { stdenv, lib, fetchFromGitHub, autoreconfHook, pkgconfig
 , libXext, libdrm, libXfixes, wayland, libffi, libX11
-, libGL
+, libGL, libGL_driver
 , minimal ? true, libva
 }:
 
@@ -27,7 +27,8 @@ stdenv.mkDerivation rec {
   enableParallelBuilding = true;
 
   configureFlags = [
-    "--with-drivers-path=${libGL.driverLink}/lib/dri"
+    # Add FHS paths for non-NixOS applications.
+    "--with-drivers-path=${libGL_driver.driverLink}/lib/dri:/usr/lib/dri:/usr/lib32/dri"
   ] ++ lib.optionals (!minimal) [ "--enable-glx" ];
 
   installFlags = [