[Bug go/64021] Empty struct vs libffi

[rth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64021

--- Comment #1 from Richard Henderson <rth at gcc dot gnu.org> ---
Oh, that should read "fail after the merge of the new libffi".

Current libffi happens to have nothing interesting in the stack
slot that's incorrectly popped, and to happens not to fail.  Not
so with the ffi_call_go rewrite.