Fix setup.py to respect numpy's parsing of libraries in site.cfg

numpy parses libraries in site.cfg by splitting on comma. We want to
maintain compatibility with that, but we've already established
os.pathname by accident. To minimize breakages, we support both.

setup.py

@@ -71,8 +71,10 @@ def parse_site_cfg():
             site['mkl']['include_dirs'].split(os.pathsep))
         lib_dirs.extend(
             site['mkl']['library_dirs'].split(os.pathsep))
+        # numpy's site.cfg splits libraries by comma, but numexpr historically split by os.pathsep.
+        # For compatibility, we split by both.
         libs.extend(
-            site['mkl']['libraries'].split(os.pathsep))
+            site['mkl']['libraries'].replace(os.pathsep, ',').split(','))
         def_macros.append(('USE_VML', None))
         print(f'FOUND MKL IMPORT')