bitbake: toasterui: process SetBRBE event

bitbake: toasterui: process SetBRBE event

Currently BRBE is known to toasterui only when build is
started. It's passed to it with BuildStarted event. This is
too late as if build fails earilier than build starts toasterui
can not inform Toaster about the failure.

Set BRBE as soon as it's provided by Toaster.
This should make toasterui to be able to inform Toaster
about early build failures, e.g. failures during recipe parsing.

(Bitbake rev: d7819508dac488a64be3caec88db285cda9599ab)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Michael Wood <michael.g.wood@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>