make sure logfile does not just append, but start a new file for a new run

launcher/simc-launcher.in

@@ -76,6 +76,10 @@ with tempfile.TemporaryDirectory() as tmpdir:
     print(' - Linking output directories...')
     os.symlink(output_dir, tmp_output_dir)
     os.symlink(output_dir, tmp_worksim_dir)
+    # also cleanup logfile if needed
+    logfile = '{outdir}/{conf}.log'.format(outdir=output_dir, conf=tmp_conf_name)
+    if os.path.exists(logfile):
+        os.remove(logfile)
 
     print(' - Linking input file...')
     os.symlink(data_path, tmp_data_path)