[PATCH v2] <shlib-compat.h>: Support compat_symbol_reference for _ISOMAC

[Florian Weimer]

* H. J. Lu:

> On Tue, Mar 2, 2021 at 12:10 PM Florian Weimer via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
>>
>> This is helpful for testing compat symbols in cases where _ISOMAC
>> is activated implicitly due to -DMODULE_NAME=testsuite and cannot
>> be disabled easily.
>>
>> ---
>> v2: Now actually tested in the situation where I need it.
>>
>
> Any particular tests which need this?

nptl/tst-cleanup4aux.c will need this once _pthread_cleanup_push,
_pthread_cleanup_pop are compatibility symbols.

Thanks,
Florian