generate_pyi: Propagate environment PATH variables to DLL directories

This facilitates .pyi generation when wrapping modules with dependencies.

Wrapping/Python/vtkmodules/generate_pyi.py

@@ -623,6 +623,15 @@ def main(argv=sys.argv):
             # the module is definitely an extension module
             modules.append(modname)
 
+    # Give all PATH environment variable entries to add_dll_directory on Windows
+    # This enable third-party libraries like OpenXR loader's DLL to be found easily.
+    if os.name == "nt":
+        for p in os.environ.get("PATH").split(';'):
+            try:
+                os.add_dll_directory(p)
+            except Exception as e:
+                print(f"Warning: Failed to add {p} as DLL search directory: ${e}")
+
     # iterate through the modules in the package
     errflag = False
     for modname in modules: