[Bug go/64999] s390x libgo test failure in TestMemoryProfiler

["ian at airs dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64999

--- Comment #41 from Ian Lance Taylor <ian at airs dot com> ---
I really don't want libbacktrace to be processor-dependent.  That makes all
uses of it more complex for no significant gain.  Maybe we should change
libbacktrace, but definitely not by making it processor-dependent.

I would prefer that changes to files like runtime/pprof/pprof.go and log/log.go
go through the master repo first.  If gccgo's runtime.Callers acts the same as
gc's runtime.Callers, then there shouldn't be any gccgo-specific need to change
those files.

Can somebody please try just editing the function callback in
runtime/go-callers.c to add one to pc when storing it in loc->pc?  I'd like to
understand why that simple change doesn't work before trying something more
complex.