CI: ssl: enable parallel builds for OpenSSL on Linux

Running the "make all" phase on my machine with -j$(nproc) shrinks the
build time from 4'52 to 1'28. It will not be that big of a change in
the CI since it looks like two CPUs are exposed, but it should still
remain a net win. Let's enable it. The install phase obviously remains
sequential however.

(cherry picked from commit c6f1498405c9d118aa7df67815d6111738c16e28)
Signed-off-by: William Lallemand <wlallemand@haproxy.org>
1 file changed