qwt in portage is at 5.2.1 which is from 2010, version 5.2.3 is out which is much more recent. I have to use qwt version 5 because of python support with pyqwt. 5.2.2/5.2.3 both contain important bug fixes. Reproducible: Always
Simply renaming the ebuild seems to compile fine
+*qwt-5.2.3 (04 Mar 2013) + + 04 Mar 2013; Justin Lecher <jlec@gentoo.org> +qwt-5.2.3.ebuild, + -qwt-6.0.1.ebuild, -qwt-6.0.1-r1.ebuild, metadata.xml: + Version Bump, #460200; build static libs, #260324 +