s3: fall back to cups-config for underlinked libs

s3: fall back to cups-config for underlinked libs

some OpenBSD systems have underlinked cups libraries. If linking against cups
alone fails, try to link against all the cups-config --libs cruft, which we
usually don't want. (bugzila #7244)
(cherry picked from commit 616e187d68e3e7b202413a96518b31d029e9563a)
(cherry picked from commit fd43cc698a7f03c4d6c48d21e88097cc5050ca8e)