Upstream defaults to cmake. This move leaves issues with the autotools build system in its wake. Patches welcome.
Apart from the fact that according to their documentation there is no mention about cmake: https://www.wireshark.org/docs/wsug_html_chunked/ChBuildInstallUnixBuild.html But it looks like they are using cmake themselves.
Upstream seems to keep cmake and autotools better in sync these days.
https://code.wireshark.org/review/gitweb?p=wireshark.git;a=commit;h=4a156da068269aae75d79cd08e579754c52a0c43 "Remove autotools build system. It has been replaced by cmake."
Fixed in the live ebuild and 2.6.0-r1. Please file a new bug report if anything is wrong with those.