opengl: Config option now specifies drivers output

pkgs/opengl/default.nix

@@ -51,6 +51,10 @@ in {
       "-Dgallium-nine=false"
     ];
 
+    preInstall = ''
+      mkdir -p $out/share
+    '' + attrs.preInstall or "";
+
     postInstall = ''
       # move drivers (just vulkan in our case and doesn't avoid LLVM)
       mkdir -p $drivers/lib
@@ -60,9 +64,6 @@ in {
       mkdir -p $osmesa/lib
         mv -t $osmesa/lib/ $out/lib/libOSMesa*
 
-      # move vendor files
-      mv $out/share/ $drivers/
-
       # Update search path used by Vulkan (it's pointing to $out but
       # drivers are in $drivers)
       for js in $drivers/share/vulkan/icd.d/*.json; do