Accept change identifier as an argument.
Accept change identifier as an argument.

This allows the buildbot to calculate the change identifier and pass it into
archive_build. This makes it easier for us to parallelize the archive_build
step.

BUG=chromium-os:12220
TEST=Verify this argument works. Verify archive_build works without the argument
     too.

Change-Id: I6b757cc7795fb6f2f24a400502fe6f70416ab44f
Reviewed-on: http://gerrit.chromium.org/gerrit/4440
Reviewed-by: Chris Sosa <959d3d631fb6f17f1b07f751372041a1edb210d1@chromium.org>
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

vmware/coreos-scripts,marineam/coreos-scripts,BugRoger/scripts,nicescale/scripts,mjg59/scripts,andrejro/coreos--scripts,vmware/coreos-scripts,mjg59/scripts,endocode/scripts,andrejro/coreos--scripts,mjg59/scripts,coreos/scripts,trnubo/scripts,smilart/scripts,bcwaldon/coreos-scripts,gtank/scripts,bcwaldon/coreos-scripts,zhang0137/scripts,fivethreeo/scripts,crawford/scripts,glevand/coreos--scripts,BugRoger/scripts,nicescale/scripts,smilart/scripts,trnubo/scripts,marineam/coreos-scripts,zhang0137/scripts,marineam/coreos-scripts,sigma/coreos-scripts,sigma/coreos-scripts,andrejro/coreos--scripts,fivethreeo/scripts,mischief/scripts,smilart/scripts,bcwaldon/coreos-scripts,BugRoger/scripts,crawford/scripts,vmware/coreos-scripts,mischief/scripts,endocode/scripts,gtank/scripts,trnubo/scripts,fivethreeo/scripts,sigma/coreos-scripts,zhang0137/scripts,nicescale/scripts,mischief/scripts,glevand/coreos--scripts,gtank/scripts,endocode/scripts,crawford/scripts,coreos/scripts