helpconfig: add invocation dir to debug output

The current WD is not supposed to matter, the invocation dir is what
should be relevant. But keep them both for debugging.

src/_pytest/helpconfig.py

@@ -109,10 +109,11 @@ def pytest_cmdline_parse() -> Generator[None, Config, Config]:
         debugfile = open(path, "w", encoding="utf-8")
         debugfile.write(
             "versions pytest-%s, "
-            "python-%s\ncwd=%s\nargs=%s\n\n"
+            "python-%s\ninvocation_dir=%s\ncwd=%s\nargs=%s\n\n"
             % (
                 pytest.__version__,
                 ".".join(map(str, sys.version_info)),
+                config.invocation_params.dir,
                 os.getcwd(),
                 config.invocation_params.args,
             )