Use shared lib of libpcap in tcpdump instead of static one.

libpcap is used by netd and tcpdump on angler build.
Size diffs on angler build image are as follows.

netd      :  290248 ->  290216 (-    32)
tcpdump   : 1301840 -> 1024376 (-277464)
libpcap.so:       0 ->  307552 (+307552)
total     :                    (+ 30056)

But libpcap is being linked by some vendors' components.
So on such builds, the size diff will be reduced more; it could be
negative possibly.

Test: building succeeded, and the image was tested on angler.
Bug: 33056637
Change-Id: Icd87c4ebc7c307a8f069adae82732e961010bf25