Avoid backslash-in-env-var entirely

test/test_environment.py

@@ -65,9 +65,8 @@ def test_overridden_path(tmp_path, capfd):
             (new_path / 'python').touch(mode=0o777)
 
             utils.cibuildwheel_run(project_dir, output_dir=output_dir, add_env={
-                # use single-quotes for new_path, because on windows, paths with backslashes
-                # are interpreted by bash as escape sequences!
-                'CIBW_ENVIRONMENT': f'''PATH='{new_path}{os.pathsep}'$PATH''',
+                'NEW_PATH': new_path,
+                'CIBW_ENVIRONMENT': f'''PATH="$NEW_PATH{os.pathsep}$PATH''',
             })
 
     assert len(os.listdir(output_dir)) == 0