Upstream moved Host.h from Support to TargetParser in LLVM 17.
This shouldn't lead to a FTBFS, since there is a forwarding include left
behind. Sadly the added deprecation warning #pragma is invalid and thus
causes a build failure right away. But since we would have to follow the
move anyway in the future, just do it right away.
Reference: d768bf994f
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Closes: #8275
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21263>