x86: re-add stack alignment check

x86: re-add stack alignment check

Commit 279840d5ea ("x86/boot: install trap handlers much earlier on
boot"), perhaps not really intentionally, removed this check. Add it
back,
- preventing it from triggering before any output is set up,
- accompanying it with a (weaker, due to its open coding of what
  get_stack_bottom() does) build time check.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>