Try closing the file stream before writing

Because Windows (and macOS?) might not support opening same temporary file twice.

pygmt/helpers/tempfile.py

@@ -61,6 +61,7 @@ def __init__(self, prefix="pygmt-", suffix=".txt"):
         args = dict(prefix=prefix, suffix=suffix, delete=False)
         with NamedTemporaryFile(**args) as tmpfile:
             self.name = tmpfile.name
+            self.close = tmpfile.close
 
     def __enter__(self):
         return self

pygmt/x2sys.py

@@ -27,6 +27,7 @@ def tempfile_from_dftrack(track, suffix):
     text file with a suffix (e.g. 'xyz').
     """
     with GMTTempFile(suffix=suffix) as tmpfile:
+        tmpfile.close()  # close the file stream
         track.to_csv(
             path_or_buf=tmpfile.name,
             sep="\t",