Add missing test helper.

Author: freakboy3742

Lib/test/support/os_helper.py

@@ -198,6 +198,24 @@ def skip_unless_symlink(test):
     return test if ok else unittest.skip(msg)(test)
 
 
+_can_hardlink = None
+
+
+def can_hardlink():
+    global _can_hardlink
+    if _can_hardlink is None:
+        # Android blocks hard links using SELinux
+        # (https://stackoverflow.com/q/32365690).
+        _can_hardlink = hasattr(os, "link") and not support.is_android
+    return _can_hardlink
+
+
+def skip_unless_hardlink(test):
+    ok = can_hardlink()
+    msg = "requires hardlink support"
+    return test if ok else unittest.skip(msg)(test)
+
+
 _can_xattr = None