I was speaking for Oracle Solaris 11.4, where CLOCK_THREAD_CPUTIME_ID is now implemented (and we don't need it in older releases). But you are right that other Solaris/SunOS versions might not have this and hence would find this useful.

I can rebase and reopen the original PR, but I cannot test it that well now that our Solaris doesn't use that part of the code (I can change the #define for testing, that should be sufficient).