std: once: use queue implementation on Xous

Use the global queue implementation of Once when running on Xous. This
gets us a thread-safe implementation, rather than using the
non-threadsafe `unsupported` implementation.

Signed-off-by: Sean Cross <sean@xobs.io>

Author: xobs

library/std/src/sys/pal/xous/mod.rs

@@ -14,8 +14,6 @@ pub mod io;
 pub mod locks;
 #[path = "../unsupported/net.rs"]
 pub mod net;
-#[path = "../unsupported/once.rs"]
-pub mod once;
 pub mod os;
 #[path = "../unix/os_str.rs"]
 pub mod os_str;

library/std/src/sys_common/once/mod.rs

@@ -25,6 +25,7 @@ cfg_if::cfg_if! {
         target_family = "unix",
         all(target_vendor = "fortanix", target_env = "sgx"),
         target_os = "solid_asp3",
+        target_os = "xous",
     ))] {
         mod queue;
         pub use queue::{Once, OnceState};