If Asterisk is built using a DESTDIR this will cause the bundled jansson
to be installed to an unexpected location and we will fail to find it.
Change-Id: Id033e2813261e0d45232383d44c6391122169548
Update the bundled jansson Makefile to do nothing during Asterisk
install, use a target that is not phony to initiate the jansson make and
install.
Change-Id: I7643cc3d39af9feba8fc0da676b646efc5f8b3bb