tests: add unreachable intrinsic to minicore

Author: workingjubilee

tests/auxiliary/minicore.rs

@@ -198,6 +198,16 @@ trait Drop {
     fn drop(&mut self);
 }
 
+pub mod hint {
+    pub use super::intrinsics::unreachable as unreachable_unchecked;
+}
+
+pub mod intrinsics {
+    #[rustc_nounwind]
+    #[rustc_intrinsic]
+    pub unsafe fn unreachable() -> !;
+}
+
 pub mod mem {
     #[rustc_nounwind]
     #[rustc_intrinsic]