Revert "std.c: openbsd sigcontext/ucontext for arm64."

This reverts commit 1585ed637d101ed16adb6b9ebdfa465299bfdb13.
f3adbe249bAndrew Kelley committed on 7/31/2023, 6:10:40 PMparent8c7eb8c
1 file changedLine totals unavailable