See attached build log.
(Please do not complain about the need for looking at the build log until you can provide an easy way to open bugs with the correct data picked out of a tinderbox log. Thanks.)
Created attachment 242009 [details]
I don't see where LDFLAGS are missing and I don't get a warning.
+ 03 Apr 2014; Tom Wijsman <TomWij@gentoo.org> +owfs-2.7_p21-r2.ebuild,
+ [QA] Revision bump. EAPI 5. Support user's CFLAGS and LDFLAGS; fixes bug
+ #331795, reported by Diego.
Thank you very much for reporting.