graphics/qt5-q3d: convert AVX2 detection hack to OPTIONS (+)

Force qt5-qmake to pass CXXFLAGS to cpu features test.
Define AVX OPTION only amd64/i386 arches due to cpu used.

Off by default to keep out-of-box behavior and allow to build
qt5-q3d and its consumes on any old processors.

Necromages, go forward! :)

PR: 255753
With hat: desktop
Sponsored by: Netzkommune GmbH