media-video/mpv: add CPU_FLAGS_X86=sse4_1 support to 9999

Requires recent GCC. Previous commit ensures that GCC is recent enough.
Useful only with vaapi.

Package-Manager: Portage-2.3.3, Repoman-2.3.1
Closes: gentoo#3718

media-video/mpv/mpv-9999.ebuild

@@ -33,6 +33,7 @@ IUSE="+alsa aqua archive bluray cdda +cli coreaudio cplugins cuda doc drm dvb
 	luajit openal +opengl oss pulseaudio raspberry-pi rubberband samba sdl
 	selinux test tools +uchardet v4l vaapi vdpau vf-dlopen wayland +X xinerama
 	+xscreensaver +xv zsh-completion"
+IUSE+=" cpu_flags_x86_sse4_1"
 
 REQUIRED_USE="
 	|| ( cli libmpv )
@@ -143,6 +144,9 @@ mpv_check_compiler() {
 		if ( use opengl || use egl ) && ! tc-has-tls; then
 			die "Your compiler lacks C++11 TLS support. Use GCC>=4.8 or Clang>=3.3."
 		fi
+		if use vaapi && use cpu_flags_x86_sse4_1 && ! tc-is-gcc; then
+			die "${PN} requires GCC for SSE4.1 intrinsics."
+		fi
 	fi
 }