tests/benchmarks: Fix operation on windows

The test script did not work on windows
since it had some trouble importing the
api module on the blender side of things.

turning the file path to the module into
a raw string literal sidesteps the
backslash issue in the path.

Differential Revision: https://developer.blender.org/D13163

Reviewed by: brecht

tests/performance/api/environment.py

@@ -235,7 +235,7 @@ class TestEnvironment:
         output_prefix = 'TEST_OUTPUT: '
 
         expression = (f'import sys, pickle, base64\n'
-                      f'sys.path.append("{package_path}")\n'
+                      f'sys.path.append(r"{package_path}")\n'
                       f'import {modulename}\n'
                       f'args = pickle.loads(base64.b64decode({args}))\n'
                       f'result = {modulename}.{functionname}(args)\n'