I edited the irssi ebuild to use the glib version that is in the current overlay. Diff is attached. Reproducible: Always Steps to Reproduce: 1. 2. 3.
Created attachment 51554 [details, diff] diff for irssi-0.8.10-rc5-r1 to compile on gentoo-bsd
Not sure about that but when libiconv and gettext are fixed in portage, irssi can be merged with the normal official ebuild (and glib2). See bug #84683
gettext and libiconv are in main portage. glib2 in overlay works out of the box (and i hope soon the one in portage will be enough) irssi works fine here.