lsof: fix builds on NetBSD 8.x and 9.x

patch-ag r. 1.14 introduced incorrect patterns that broke builds.
(Formal releases since 8.x do not include a "patch level"/"teeny"
number, and the change also failed to match releases with "_STABLE"
or "_RCx".) Addresses PR 58199 from Stefan Schaeckeler.

(gutteridge)