Revert "chromium: remove preferLocalBuild"
This reverts commit fdb5cf8107d6ecb5c775c2ad026551dbd11248f1.
The reason I'm reverting this is that the implications this had on the
IO load of Hydra are fixed by c92dbffeac75afe93c05c1ef216e927f075755c5.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>