Fix test_case_insensitive_build_tree_inventory failure on OSX.
* bzrlib/tests/test_transform.py: (TestBuildTree.test_case_insensitive_build_tree_inventory): This should have fail earlier, but it fails only since bzr.dev@4216 (with _cicp_canonical_relpath activated for OSX). Anyway, this test requires a true case sensitive file system.