Remove os.mknod in deepmd/dump

method os.mknod is not supported for MacOS and Windows.

Author: AnguseZhang

dpdata/deepmd/raw.py

@@ -74,5 +74,7 @@ def dump (folder, data) :
     except OSError:
         pass
     if data.get("nopbc", False):
-        os.mknod(os.path.join(folder, "nopbc"))
+        #os.mknod(os.path.join(folder, "nopbc"))
+        with open(os.path.join(folder, "nopbc"), "w") as fw_nopbc:
+            fw_nopbc.write("")