Ebuild depends on x11-libs/libva[X,opengl] but opengl use flag isn't supported upstream

[nagmat84]

The ebuid declares a runtime dependency for x11-libs/libva[X,opengl]. But x11-libs/libva does not support the opengl use flag, see https://packages.gentoo.org/packages/media-libs/libva.

[i-rinat]

The issue you are describing doesn't seems to be fixable here.
I recommend to send this bugreport to the Gentoo bugtracker, as there are much higher chances it will be at least seen there. I doubt Gentoo maintainers closely monitor this place.