Make the lib64 symlink relative (#33)

Fixes #35

---------

Co-authored-by: Brett Cannon <brett@python.org>

microvenv.py

@@ -55,7 +55,7 @@ def create(env_dir=".venv"):
         # There is no guarantee the sysconfig scheme will produce a `lib`
         # directory.
         if lib_path.is_dir() and not lib64_path.exists():
-            lib64_path.symlink_to(lib_path, target_is_directory=True)
+            lib64_path.symlink_to("lib", target_is_directory=True)
 
     for executable_name in (
         "python",

test_microvenv.py

@@ -79,6 +79,8 @@ def test_lib64(full_venv, micro_venv):
         assert micro_lib64.exists()
         assert micro_lib64.is_symlink()
         assert micro_lib64.resolve() == (micro_venv / "lib")
+        # pathlib.Path.readlink() was added in Python 3.9.
+        assert os.readlink(micro_lib64) == "lib"
 
 
 @pytest.mark.parametrize(