If either gcc or clang are missing, skip doing those builds.
This allows a setup to only do, e.g. gcc tests.
Cc: stable@dpdk.org
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Luca Boccassi <bluca@debian.org>
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>