kernel-yocto: propagate configuration errors to bbclass
As pointed out by klapperichpaul@johndeere.com, missing configuration
fragments were being picked up twice, once by the tools and once by the
bbclass. Unfortunately, the tools error message was being detected as
configs, and hence no error was reported at all.
Rather than catching the output of the tools, we can instead check the
return code and propagate the error message from the tools directly to
the user.
[YOCTO #11649]
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com> Signed-off-by: Ross Burton <ross.burton@intel.com>