[DEPENDS] Allow to limit the jobs when building packages with ninja
Pass the JOBS variable to ninja to allow for limiting the number of
jobs when building the packages.
cd depends make build-osx # This target should be benefit the most from this diff
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D4875