chromium: Precompile pycs instead of deleting.

This is more of an attempt rather than a real fix (or maybe it is? let's
see) for the corrupted .pyc files during build. I believe the reason we
get these are likely due to several instances of the Python interpreter
that run in parallel and one of these processes might still be writing
the .pyc file.

So, rather than deleting all .pyc files, we now precompile then in order
to avoid any build process trying to generate any .pyc file.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>