Meshing: Mage: Fix libbief extention under windows system.

src/Meshing/Mage.py

@@ -53,10 +53,12 @@ class MeshingWithMage(AMeshingTool):
         self._init_c_output_bief()
 
     def _lib_path(self):
+        ext = "so" if os.name == "posix" else "dll"
+
         return os.path.abspath(
             os.path.join(
                 os.path.dirname(__file__),
-                "..", "..", "..", "mage", "libbief.so"
+                "..", "..", "..", "mage", f"libbief.{ext}"
             )
         )