panic_unwind: support unwinding on xous

Now that `unwind` supports Xous, enable unwinding panics on Xous.

Signed-off-by: Sean Cross <[email protected]>

Author: xobs

library/panic_unwind/src/lib.rs

@@ -49,6 +49,7 @@ cfg_if::cfg_if! {
     } else if #[cfg(any(
         all(target_family = "windows", target_env = "gnu"),
         target_os = "psp",
+        target_os = "xous",
         target_os = "solid_asp3",
         all(target_family = "unix", not(target_os = "espidf")),
         all(target_vendor = "fortanix", target_env = "sgx"),