Add base and root bindings to pre test command

Author: Nig3l

src/rez/package_test.py

@@ -455,6 +455,8 @@ def _pre_test_commands(executor):
 
                 with executor.reset_globals():
                     executor.bind("this", variant)
+                    executor.bind('root', variant.root)
+                    executor.bind('base', executor.normalize_path(package.base))
                     executor.bind("test", RO_AttrDictWrapper(test_ns))
                     executor.execute_code(pre_test_commands)