support/scripts/pkg-stats: run main function only if called as script

The __name__ == '__main__' guard allows importing pkg-stats as a
module using importlib, circumventing the normal module filename
requirements. This in turn makes it possible to test/debug individual
functions.

Signed-off-by: Fiona Klute <fiona.klute@gmx.de>
Signed-off-by: Arnout Vandecappelle <arnout@rnout.be>
(cherry picked from commit 8cde69e101)
Signed-off-by: Thomas Perale <thomas.perale@mind.be>

support/scripts/pkg-stats

@@ -1334,7 +1334,7 @@ def is_newer_version_available(pkg):
     )
 
 
-def __main__():
+def main():
     global cvecheck
 
     args = parse_args()
@@ -1403,4 +1403,5 @@ def __main__():
         dump_json(packages, defconfigs, stats, date, commit, args.json)
 
 
-__main__()
+if __name__ == '__main__':
+    main()