Hello. I understand your concern and thank you for brining it in. If I understand the comment at https://github.com/Windows-on-ARM-Experiments/newlib-cygwin/blob/woarm64/winsup/cygwin/lib/_cygwin_crt0_common.cc#L123 correctly, this can happen when Cygwin application is linked with non-Cygwin stdlib. I don't know if this is a legit use-case supported on x64 but, nevertheless, I'd IMO suggest to consider it as an extended use-case that is not implemented yet. If that is OK, I can add that information to the patch commit message and/or TODO comment in the code...
Radek
