Fix perf path in codegen

[edopao]

This code change addresses the following error:

           callsite_stream.write(
>               '''__state->report.save("{path}/perf", __HASH_{name});'''.format(path=sdfg.build_folder.replace(
                    '\\', '/'),
                                                                                 name=sdfg.name), sdfg)
E           TypeError: Path.replace() takes 2 positional arguments but 3 were given