mathematica: Prefer building locally (#100856)

There is little benefit to copying a 4GB tarball over the network,
just to perform an I/O-bound operation and then copy the
multi-gigabyte result back.

pkgs/applications/science/math/mathematica/default.nix

@@ -144,6 +144,9 @@ stdenv.mkDerivation rec {
   '';
 
   dontBuild = true;
+  
+  # This is primarily an IO bound build; there's little benefit to building remotely.
+  preferLocalBuild = true;
 
   # all binaries are already stripped
   dontStrip = true;