Check the attached build log, it seems like it's related to -Werror so for a more future-proof patch I'd just disable that to begin with.
Created attachment 175265 [details] Build log
+ 15 Feb 2009; Peter Alfredsen <loki_val@gentoo.org> tos-uisp-1.1.15.ebuild: + Add Wno-error to flags for bug 250957 +