cros_chrome_make: Flag to control ccache.
cros_chrome_make: Flag to control ccache.

Running the compile with ccache enabled is interfering with some
other tools. Disable ccache by default and add a flag to re-enable.

BUG=None
TEST=Ran for x86-alex with ccache enabled, disabled and default.
  Portage log shows the expected FEATURES. Other tool no longer hangs
  with ccache disabled.

Change-Id: Ifb0512dae6a8968809e4d481236d996d59675d48
Reviewed-on: https://gerrit.chromium.org/gerrit/14288
Reviewed-by: Chris Masone <98e3d65c6b0e9e2391eb4c2e8b1e572b77e544ed@chromium.org>
Commit-Ready: Chris Wolfe <4f23406e03c8ffaccefe8744212d3543c02e8d87@chromium.org>
Tested-by: Chris Wolfe <4f23406e03c8ffaccefe8744212d3543c02e8d87@chromium.org>

marineam/coreos-dev-util,coreos/dev-util,marineam/coreos-dev-util,mgireesh05/dev-util,mgireesh05/dev-util,coreos/dev-util,mgireesh05/dev-util,coreos/dev-util