Documentation installed by make install. Fixed for me by adding to src_prepare(): sed -i '/ doc/d' qwt.pro || die
commit fe5a79f2b150f550213f8e22d41fdf0a826a0b9a Author: Justin Lecher <jlec@gentoo.org> Date: Sun Jan 15 16:56:42 2017 +0000 x11-libs/qwt: Backport changes Fixes doc installation Gentoo-Bug: https://bugs.gentoo.org/show_bug.cgi?id=595938 Package-Manager: Portage-2.3.3, Repoman-2.3.1 Signed-off-by: Justin Lecher <jlec@gentoo.org> https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=fe5a79f2b150f550213f8e22d41fdf0a826a0b9a