rts: Prefer darwin-specific getCurrentThreadCPUTime
macOS Catalina now supports a non-POSIX-compliant version of clock_gettime which cannot use the clock_gettime codepath.
Fixes #17906 (closed).
macOS Catalina now supports a non-POSIX-compliant version of clock_gettime which cannot use the clock_gettime codepath.
Fixes #17906 (closed).