On some build environment we may want to limit number of parallel jobs since
ninja-build runs ncpus jobs by default, it may too many since g++ eats very
huge memory.
So support --jobs <njobs> just like on rpm build script.
Signed-off-by: Takuya ASADA <syuu@scylladb.com>
Message-Id: <20180425205439.30053-1-syuu@scylladb.com>
(cherry picked from commit 782ebcece4)