Backport of "systemclock: fix usage of __STDC_NO_ATOMICS__" into 1.24
requested to merge gstreamer-backport-bot/gstreamer:mr-6848-backport-into-1.24-fix-stdc-no-atomics-typo into 1.24
Backport of !6848 (merged) "systemclock: fix usage of STDC_NO_ATOMICS".
Commits:
- 0e3e688b systemclock: fix usage of STDC_NO_ATOMICS