Set CC.host and CXX.host to clang as well on the clang bots.

Set CC.host and CXX.host to clang as well on the clang bots.

This allows us to get rid of the _toolset=="target" checks in
common.gypi.

I personally find it cleaner to default both CC.target and CC.host
to CC and let the cross-compiler people set both these env vars,
but piman didn't like that suggestion.
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=93413

[Nico, 2011-07-21 02:07:38]

This should also enable mac bots that build using make build & clang. I will
update the clang wiki page once this is in.

[Marc-Antoine Ruel (Google), 2011-07-21 02:14:20]

I can only rubberstamp this since it's outside my knowledge area.
rubberstamp lgtm