[DEPENDS] Make bdb, dbus, event, miniupnpc, zmq packages build parallel

Summary:
As per title. The install phase is left intact as there is almost
nothing to gain here.

Test Plan:

cd depends
make

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D4866