Fix --static-pcap-only test on Solaris 10.

(Same as in tcpdump.)

Before:

checking for pcap-config... ../libpcap/pcap-config
grep: illegal option -- q
Usage: grep -hblcnsviw pattern file . . .
checking for pcap_loop... no
configure: error: This is a bug, please follow...

After:

checking for pcap-config... ../libpcap/pcap-config
checking for pcap_loop... yes