Do not attempt setup.py clean for failed pep517 builds

Fixes pypa#6642

Author: sbidoul

news/6642.bugfix

@@ -0,0 +1,2 @@
+Do not attempt to run ``setup.py clean`` after a ``pep517`` build error,
+since a ``setup.py`` may not exist in that case.

src/pip/_internal/wheel_builder.py

@@ -231,11 +231,12 @@ def _build_one_inside_env(
                     req.name, e,
                 )
         # Ignore return, we can't do anything else useful.
-        _clean_one(req, global_options)
+        if not req.use_pep517:
+            _clean_one_legacy(req, global_options)
         return None
 
 
-def _clean_one(req, global_options):
+def _clean_one_legacy(req, global_options):
     # type: (InstallRequirement, List[str]) -> bool
     clean_args = make_setuptools_clean_args(
         req.setup_py_path,