Fix build failure on systems without clock_gettime (#4655)
Fix build failure on systems without clock_gettime (#4655)

The #if was mistakenly placed before the function signature rather than
after when this code was refactored in d6add5e. As a result, a
subsequent clang format misformatted the code in 3aa03bb.

Closes #3896
swoole/swoole-src,swoole/swoole-src,swoole/swoole-src,swoole/swoole-src,swoole/swoole-src,swoole/swoole-src,swoole/swoole-src