Use futex_waitv on recent Linux kernels for better reimplementation of WaitForMultipleObjectsEx

[anisse]

Since Linux 5.16 (21 months+ ago), Linux has a new syscall called futex_waitv, added specifically for the Wine reimplementation of WaitForMultipleObjectsEx. It seems that the dotnet runtime has an InternalWaitForMultipleObjectsEx which uses libc pthread locking instead.

It might be worth it to explore migrating to the new syscall for the use of the dotnet runtime.

Looking at a big dotnet application, I see that in some cases contention can be quite high. I have nothing to share specifically here (otherwise this would be an issue), but it seemed like a missed opportunity during my explorations.