opcache: Use O_TMPFILE file lock if available

[crrodriguez]

Use O_TMPFILE if the kernel supports it to create the lock fd, this
has multiple advantages including not having to worry about naming,
permissions and the assurance that it will always go away cleanly
even on abnormal termination.

[ramsey]

Since I had to go look up O_TMPFILE, I'll drop this link here for others (and my future self 😉): https://www.gnu.org/software/libc/manual/html_node/Open_002dtime-Flags.html#index-O_005fTMPFILE

[crrodriguez]

Since I had to go look up O_TMPFILE, I'll drop this link here for others (and my future self 😉): https://www.gnu.org/software/libc/manual/html_node/Open_002dtime-Flags.html#index-O_005fTMPFILE

This is not the correct manual page to reference. Use https://man7.org/linux/man-pages/man2/open.2.html.

[ramsey]

Thanks for the clarification!

[dstogov]

I don't see any problems.
Sorry, I missed this PR in May.