Fall back to ppoll if ppoll_time64 fails with ENOSYS.
Fixes commit 370da8a121 ("nptl: Fix
tst-cancel30 on sparc64").
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
As indicated by sparc kernel-features.h, even though sparc64 defines
__NR_pause, it is not supported (ENOSYS). Always use ppoll or the
64 bit time_t variant instead.
