Currently if a task generates the same output with different timestamps,
hasequiv won't detect it but reproducibile builds will fail tests due
to the different timestamps.
Add do_package timestamps to the hash when reproducibile builds are enabled
to avoid this.
(From OE-Core rev: 11e8200ccec765ff6a4263e06512e5751eca261a)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>