[Bug go/68562] morestack misaligns stack on x86_64

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68562

--- Comment #9 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(I've found the cause of the build problem: a stale /usr/lib/go directory)

Your patch fixes the alignment bug. Many thanks.