Override setuptools copy_extensions_to_source() to keep our stubs

This is needed due to setuptools 64.0.0 implementing PEP 660 and
circumventing usage of `write_stub_file` in `copy_extensions_to_source`
(see: pypa/setuptools#3392)

In turn, we require setuptools 64.0.0 or higher.

hpy/devel/__init__.py

@@ -112,6 +112,8 @@ def write_stub(resource, pyfile):
             if resource.endswith(".hpy.so"):
                 log.info("stub file already created for %s", resource)
                 return
+            else:
+                log.info("stub resource didn't match for %s", resource)
             write_stub.super(resource, pyfile)
 
     def build_ext_sanity_check(self, build_ext):
@@ -365,6 +367,24 @@ def write_stub(self, output_dir, ext, compile=False):
                     ext_file=ext_file, module_name=module_name)
                 )
 
+    def copy_extensions_to_source(self):
+        """Override from setuptools 64.0.0 to copy our stub instead of recreating it."""
+        build_py = self.get_finalized_command('build_py')
+        build_lib = build_py.build_lib
+        for ext in self.extensions:
+            inplace_file, regular_file = self._get_inplace_equivalent(build_py, ext)
+
+            # Always copy, even if source is older than destination, to ensure
+            # that the right extensions for the current Python/platform are
+            # used.
+            if os.path.exists(regular_file) or not ext.optional:
+                self.copy_file(regular_file, inplace_file, level=self.verbose)
+
+            if ext._needs_stub:
+                source_stub = os.path.join(build_lib, *ext._full_name.split('.')) + '.py'
+                inplace_stub = self._get_equivalent_stub(ext, inplace_file)
+                self.copy_file(source_stub, inplace_stub, level=self.verbose)
+
     def get_export_symbols(self, ext):
         """ Override .get_export_symbols to replace "PyInit_<module_name>"
             with "HPyInit_<module_name>.

pyproject.toml

@@ -1,3 +1,3 @@
 [build-system]
-requires = [ "setuptools>=40.6.0", "setuptools-scm[toml]>=6.0", "wheel>=0.34.2",]
+requires = [ "setuptools>=64.0", "setuptools-scm[toml]>=6.0", "wheel>=0.34.2",]
 build-backend = "setuptools.build_meta"

setup.py

@@ -162,5 +162,5 @@ def get_scm_config():
     },
     use_scm_version=get_scm_config,
     setup_requires=['setuptools_scm'],
-    install_requires=['setuptools>=60.2'],
+    install_requires=['setuptools>=64.0'],
 )