Add a short section recommending the use of buildhistory to compare
the build output before and after migration.
(From yocto-docs rev: e4a83dadbda563e08302055538203c9b1ac9e992)
Signed-off-by: Paul Eggleton <paul.eggleton@microsoft.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>