A package builds with -j1 unless it sets PKG_BUILD_PARALLEL, and 171 of
the 220 packages do not set it. These three gain the most from the job
server on a cold build of this tree:
mtd-utils 24.77 s -> 6.43 s
libsepol 17.99 s -> 2.18 s
libselinux 7.82 s -> 1.89 s
mtd-utils runs while nothing else does, so its 18 s count against the
wall clock in full.
Each one builds three times out of three with the job server, and each
build writes a tree that is identical to the one a serial build writes.
nftables gains as well, 17.9 s to 13.0 s, but it is left alone: its
build directory differs between two serial builds, so the check that
covers the other three says nothing about it.
Signed-off-by: John Crispin <john@phrozen.org>