[libc-tests] Don't test sizeof(jmp_buf) This test is not useful. There is an explicit size test in the Zircon libc build itself already. Bug: 125629 Change-Id: Ib83f14c78e2054e279d84db3cc487114f8615265 Reviewed-on: https://fuchsia-review.googlesource.com/c/libc-tests/+/846636 Fuchsia-Auto-Submit: Roland McGrath <mcgrathr@google.com> Reviewed-by: Alex Brachet <abrachet@google.com> Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>