nixpkgs/pkgs/servers/x11/xorg/xorgserver-dri-path.patch

diff -Naur xorg-server-1.12.2-orig/glx/glxdricommon.c xorg-server-1.12.2/glx/glxdricommon.c
--- xorg-server-1.12.2-orig/glx/glxdricommon.c	2012-05-17 13:09:02.000000000 -0400
+++ xorg-server-1.12.2/glx/glxdricommon.c	2012-07-14 14:57:37.972791909 -0400
@@ -219,10 +219,14 @@
     int i;
     void *driver;
     char filename[PATH_MAX];
+    char *real_dri_driver_path;
     const __DRIextension **extensions;
 
+    real_dri_driver_path = getenv("XORG_DRI_DRIVER_PATH");
+    if (!real_dri_driver_path) real_dri_driver_path = dri_driver_path;
+
     snprintf(filename, sizeof filename, "%s/%s_dri.so",
-             dri_driver_path, driverName);
+             real_dri_driver_path, driverName);
 
     driver = dlopen(filename, RTLD_LAZY | RTLD_LOCAL);
     if (driver == NULL) {