Better to error as early as possible rather than experience strange behavior
resulting from the use of the largely useless stock bitbake.conf/base.bbclass.
(Bitbake rev: 641e6cf3ec3ab4d26929cf4d2a3704ff07eed4d6)
Signed-off-by: Chris Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>