Set Distribution.has_ext_modules to True

Ensure `setuptools` knows our package has extension modules. Even though
it is not totally obvious they are there.

python/cucim/setup.py

@@ -1,5 +1,16 @@
 # Copyright (c) 2023, NVIDIA CORPORATION.
 
 from setuptools import setup
+from setuptools.dist import Distribution as _Distribution
 
-setup()
+
+# As we vendored a shared object that links to a specific Python version,
+# make sure it is treated as impure so the wheel is named properly.
+class Distribution(_Distribution):
+    def has_ext_modules(self):
+        return True
+
+
+setup(
+    distclass=Distribution,
+)