update-doxygen.sh: update local copy of workspace rather than checking it out fresh every time

update-doxygen.sh: update local copy of workspace rather than checking it out fresh every time
Committed: https://code.google.com/p/skia/source/detail?r=4590

[epoger, 2012-07-12 23:09:54]

I ran some tests locally, and it seems to work; it should save the unnecessary
network and server load of downloading EVERYTHING, every time.

[rmistry, 2012-07-12 23:31:31]

LGTM

Thanks for catching this.

[epoger, 2012-07-12 23:35:09]

Ubet.  It will require changes to housekeeping_factory.py to make use of this;
let's discuss tomorrow.