db: add switch for building database verification

db: add switch for building database verification

Add switch for building database verification, enable
this, it will solve the following issue:

root@qemux86-64:~# db_verify /var/lib/rpm/Packages
db_verify: BDB0571 library build did not include support for database verification
BDB5105 Verification of /var/lib/rpm/Packages failed.

(From OE-Core rev: a785157c7d78bd4becdc03c93a21a5dba37015b9)

Signed-off-by: Wenlin Kang <wenlin.kang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>