Don't create infer-out directory or logs unless analyzing something.

Summary:
This will stop Infer from creating an `infer-out` directory when just running `infer`.

(I run `infer` without any arguments somewhat often to look at documenting.)

One downside to this is that there will be no logs when running Infer without any commands - is this bad?
Closes https://github.com/facebook/infer/pull/240

Reviewed By: cristianoc

Differential Revision: D2829752

Pulled By: jeremydubreil

fb-gh-sync-id: 6827ef9

infer/lib/python/infer

@@ -129,19 +129,19 @@ def main():
             capture_module_name != 'analyze'):
         analyze.remove_infer_out(args.infer_out)
 
-    analyze.create_results_dir(args.infer_out)
+    if imported_module:
+        analyze.create_results_dir(args.infer_out)
 
-    configure_logging(args.infer_out, args.log_to_stderr)
-    logging.info('Running command %s', ' '.join(sys.argv))
-    logging.info('Path to infer script %s (%s)', __file__,
+        configure_logging(args.infer_out, args.log_to_stderr)
+        logging.info('Running command %s', ' '.join(sys.argv))
+        logging.info('Path to infer script %s (%s)', __file__,
                  os.path.realpath(__file__))
-    logging.info(analyze.get_infer_version())
-    logging.info('Platform: %s', platform.platform())
-    logging.info('PATH=%s', os.getenv('PATH'))
-    logging.info('SHELL=%s', os.getenv('SHELL'))
-    logging.info('PWD=%s', os.getenv('PWD'))
+        logging.info(analyze.get_infer_version())
+        logging.info('Platform: %s', platform.platform())
+        logging.info('PATH=%s', os.getenv('PATH'))
+        logging.info('SHELL=%s', os.getenv('SHELL'))
+        logging.info('PWD=%s', os.getenv('PWD'))
 
-    if imported_module:
         capture_exitcode = imported_module.gen_instance(args, cmd).capture()
         if capture_exitcode != os.EX_OK:
             logging.error('Error during capture phase, exiting')