Horizon OS support (#448)

Author: Meziu

src/backtrace/libunwind.rs

@@ -157,7 +157,8 @@ mod uw {
         #[cfg(all(
             not(all(target_os = "android", target_arch = "arm")),
             not(all(target_os = "freebsd", target_arch = "arm")),
-            not(all(target_os = "linux", target_arch = "arm"))
+            not(all(target_os = "linux", target_arch = "arm")),
+            not(all(target_os = "horizon", target_arch = "arm"))
         ))]
         pub fn _Unwind_GetIP(ctx: *mut _Unwind_Context) -> libc::uintptr_t;
 
@@ -204,13 +205,15 @@ mod uw {
     #[cfg(any(
         all(target_os = "android", target_arch = "arm"),
         all(target_os = "freebsd", target_arch = "arm"),
-        all(target_os = "linux", target_arch = "arm")
+        all(target_os = "linux", target_arch = "arm"),
+        all(target_os = "horizon", target_arch = "arm")
     ))]
     pub use self::arm::*;
     #[cfg(any(
         all(target_os = "android", target_arch = "arm"),
         all(target_os = "freebsd", target_arch = "arm"),
-        all(target_os = "linux", target_arch = "arm")
+        all(target_os = "linux", target_arch = "arm"),
+        all(target_os = "horizon", target_arch = "arm")
     ))]
     mod arm {
         pub use super::*;