Well. RHEL 7 is Redhat Enterprise Linux 7 (like Centos 7) and was released in 2014 and is still in maintenance support.
Its extended lifecycle report will end 30 June 2028.

gcc 4.8.5 was released in 2015, eight years ago, and very much alive.

When I see the TZ source code, it is coded for some MUCH older compilers.

I would not call it an old system, though I am in process of moving my servers to RHEL 9.3, the current Redhat release.

The fix below does it.

Nobody else admits to running such old compilers and systems! ;^>

I would reduce that test to:

#if __STDC_VERSION__ < 199901
# define restrict
#endif