Re-revert "chromium: remove preferLocalBuild".

This reverts commit 26f024626c45dcc2fd82f91f6c0dea63521d8bc4.

I actually wasn't reading the "remove" in the commit message, so sorry
for the brainfart/noise.

Signed-off-by: aszlig <[e-mail]>

pkgs/applications/networking/browsers/chromium/source/default.nix

···
       "$main/content/browser/browser_main_loop.cc"
   '';
 
-  preferLocalBuild = true;
-
   passthru = {
     inherit version channel;
     plugins = fetchurl binary;