(lib/sleep_until) add vxworks (os) clock_nanosleep impl

Author: dvdsk

library/std/src/sys/pal/unix/thread.rs

@@ -313,6 +313,7 @@ impl Thread {
         target_os = "dragonfly",
         target_os = "hurd",
         target_os = "fuchsia",
+        target_os = "vxworks",
         target_vendor = "apple"
     )))]
     pub fn sleep_until(deadline: Instant) {
@@ -334,6 +335,7 @@ impl Thread {
         target_os = "dragonfly",
         target_os = "hurd",
         target_os = "fuchsia",
+        target_os = "vxworks",
     ))]
     pub fn sleep_until(deadline: crate::time::Instant) {
         let mut ts = deadline

library/std/src/thread/mod.rs

@@ -894,6 +894,7 @@ pub fn sleep(dur: Duration) {
 /// | Dragonfly | [clock_nanosleep] (Monotonic Clock)]                                 |
 /// | Hurd      | [clock_nanosleep] (Monotonic Clock)]                                 |
 /// | Fuchsia   | [clock_nanosleep] (Monotonic Clock)]                                 |
+/// | Vxworks   | [clock_nanosleep] (Monotonic Clock)]                                 |
 /// | Darwin    | [mach_wait_until]                                                    |
 /// | WASI      | [subscription_clock]                                                 |
 /// | Other     | `sleep_until` uses [`sleep`] and does not issue a syscall itself     |