All flags passed to --enable-gui before "gtk" are overriden : it's a concern for "fbcon" and "dump". Reproducible: Always
Created attachment 363148 [details, diff] ebuild patch
*** Bug 499396 has been marked as a duplicate of this bug. ***
I confirm the problem. The patch has solved the problem. Please apply it to the current ebuilds in portage.
[master d716d7a] www-plugins/gnash: Disable optional gconf and gstreamer:0.10 support (#594884), prevent sandbox violations (#591014), handle gui options properly (#491120), use new ways for handling ffmpeg and openssl providers. 1 file changed, 288 insertions(+) create mode 100644 www-plugins/gnash/gnash-0.8.10_p20160329-r1.ebuild