[Bug go/66303] runtime.Caller() returns infinitely deep stack frames on s390x

[vogt at linux dot vnet.ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66303

--- Comment #9 from Dominik Vogt <vogt at linux dot vnet.ibm.com> ---
The problem is reproduceable with the makecontext C testcases in Glibc (with
some manual intervention).  So, this isn't a Go related problem.  Our analysis
so far seems to indicate that it's a bug in the s390x specific code of Glibc or
maybe the s390x unwinding code in libgcc (less likely).  We'll take care of the
problem.