[PATCH] nptl: Add test for callee-saved register restore in pthread_exit

[Florian Weimer]

* Florian Weimer:

> GCC PR 83641 results in a miscompilation of libpthread, which
> causes pthread_exit not to restore callee-saved registers before
> running destructors for objects on the stack.  This test detects
> this situation:
>
> info: unsigned int, direct pthread_exit call
> tst-thread-exit-clobber.cc:80: numeric comparison failure
>    left: 4148288912 (0xf741dd90); from: value
>   right: 1600833940 (0x5f6ac994); from: magic_values.v2
> info: double, direct pthread_exit call
> info: unsigned int, indirect pthread_exit call
> info: double, indirect pthread_exit call
> error: 1 test failures
>
> (cherry picked from commit 579396ee082565ab5f42ff166a264891223b7b82)

Please disregard.  Should have gone to libc-stable.