configure.ac: disable enable_gallium_llvm in the !x86 case

Already implicitly handled throughout, but keep it clear and disable
gallium-llvm. This change should be a no-op.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Tobias Droste <tdroste@gmx.de>
(cherry picked from commit ce65cc1f1f648f17d9284e65f1ad69be647de3d3)
1 file changed