There is a story for OpenSSL build to be broken for `make -j`. Gentoo-
and various other people proposed fixes, at least from 2008, but for
some reasons (patch does not work with BSD make, upstream forgot to
apply, etc) they are not applied to main codebase.

What we can do is to "cherry-pick" the patch from Gentoo to speed-up
OpenSSL build. On a typical 8-cores i7 node, with the following test
buildout:

    [buildout]
    extends =
      slapos/stack/slapos.cfg
      slapos/component/openssl/buildout.cfg

after full build

                    time (rm -rf parts/openssl && ./bin/buildout install openssl)

    MAKEFLAGS=-j1   1m48s
    MAKEFLAGS=-j8   0m53s

and the timing does not subtract time to e.g. download the package from
network, so the building speedup itself is even more.

/cc @kazuhiko