Give executable permissions to GPX executable

On MacOS it apparently didn't maintain them from the zip file.

X3GWriter.py

@@ -4,6 +4,7 @@
 import configparser #To write a CFG file as configuration for GPX.
 import math #For PI.
 import os
+import stat #To give execute permissions to GPX.
 import subprocess
 import tempfile
 import typing
@@ -106,6 +107,7 @@ def gpx_executable(self):
         result = os.path.expanduser(result)
         result = os.path.expandvars(result)
         Logger.log("d", "GPX executable: {executable_file}".format(executable_file=result))
+        os.chmod(result, stat.IXUSR | stat.IRUSR | stat.IRGRP | stat.IROTH)
         return result
 
     ##  Gets the command that we need to call GPX with.
@@ -230,4 +232,4 @@ def write_cfg(self, cfg_stream):
         parser["machine"]["timeout"] = "20" #Let's just always home at most 20 seconds. This is what GPX uses for all built-in printers.
         #parser["machine"]["steps_per_mm"] = ? #I think the steps_per_mm per axis will override this.
 
-        parser.write(cfg_stream)
+        parser.write(cfg_stream)