kernel-yocto.bbclass: Support config fragments with externalsrc
The merging of config fragments is performend in the do_kernel_configme
task and so config fragments will not be supported when this task is
removed from the dependency tree.
kernel-yocto adds additional tasks which may modify the source directory
to SRCTREECOVEREDTASKS so that they are removed when using externalsrc.
However, do_kernel_configme should be safe to use, the only modification
to the source tree is the potential creation of the '.kernel-meta'
directory and the '.metadir' file.
Signed-off-by: Paul Barker <pbarker@konsulko.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
