Disable normal HashMap test on OS X

Implementing random number generation on OS X will require special-casing the
'openat' system call to special-case reading from /dev/urandom

Author: Aaron1011

tests/run-pass/hashmap.rs

@@ -28,7 +28,12 @@ fn test_map<S: BuildHasher>(mut map: HashMap<i32, i32, S>) {
 
 fn main() {
     let _map : HashMap<i32, i32, BuildHasherDefault<collections::hash_map::DefaultHasher>> = Default::default();
-    let map_normal: HashMap<i32, i32> = HashMap::new();
 
-    test_map(map_normal);
+    // TODO: Implement random number generation on OS X
+    if cfg!(not(target_os = "darwin")) {
+        let map_normal: HashMap<i32, i32> = HashMap::new();
+        test_map(map_normal);
+    } else {
+        test_map(_map);
+    }
 }