perl-cross makes it easy to cleanly disable the use of Berkeley DB if desired,
so add a PACKAGECONFIG for this.
More of the dependencies (such as gdbm) can be controlled in the same way, but
Berkeley DB is a prime contender: it's a large library which we have to ship an
old release for due to licensing issues, so there are users who may want to
strip it out of builds entirely.
Signed-off-by: Ross Burton <ross.burton@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
