Disable GUI if USE=-gui

--- a/setup.py	2020-06-27 00:24:01.872723504 +0100
+++ b/setup.py	2020-06-27 00:30:12.885365693 +0100
@@ -185,7 +185,6 @@
     entry_points={  # Optional
         'console_scripts': [
             'nuxhashd=nuxhash:nuxhashd',
-            'nuxhash-gui=nuxhash:nuxhash_gui'
         ],
     },