libgo: correct typo in USE_LIBFFI AM_CONDITIONAL

Only affects the case of passing --without-libffi to configure.

Fixes https://gcc.gnu.org/PR90635

Change-Id: I903fbb5b3858b242fa52a240a4c34fa70390a1e0
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/178998
Reviewed-by: Cherry Zhang <cherryyz@google.com>
2 files changed