webkitgtk: Add /run/opengl-driver to bubblewrap bind mounts

Without access to the `/run/opengl-driver` directory, webkit fails to
create an EGL context, since it can't identify a suitable EGL
vendor. This results in a blank window and the following error output:

Cannot get default EGL display: EGL_BAD_PARAMETER
Cannot create EGL context: invalid display (last error: EGL_SUCCESS)

pkgs/development/libraries/webkitgtk/fix-bubblewrap-paths.patch

@@ -10,14 +10,15 @@ diff -ru old/webkitgtk-2.26.0/Source/WebKit/UIProcess/Launcher/glib/BubblewrapLa
          { SCMP_SYS(move_pages), nullptr },
          { SCMP_SYS(mbind), nullptr },
          { SCMP_SYS(get_mempolicy), nullptr },
-@@ -724,6 +724,10 @@
+@@ -724,6 +724,11 @@
          "--ro-bind-try", "/usr/local/lib64", "/usr/local/lib64",
 
          "--ro-bind-try", PKGLIBEXECDIR, PKGLIBEXECDIR,
 +
 +        // Nix Directories
 +        "--ro-bind", "@storeDir@", "@storeDir@",
 +        "--ro-bind", "/run/current-system", "/run/current-system",
++        "--ro-bind", "/run/opengl-driver", "/run/opengl-driver",
      };
      // We would have to parse ld config files for more info.
      bindPathVar(sandboxArgs, "LD_LIBRARY_PATH");