Add an explicit logfile rollover at the beginning of each Tulsi bazel build.

The RotatingFileHandler normally only rolls over when the log file reaches
a certain size, which we don't specify anyway. This will enable us to have
separate files for each build.

PiperOrigin-RevId: 185406226

src/TulsiGenerator/Scripts/tulsi_logging.py

diff --git a/src/TulsiGenerator/Scripts/tulsi_logging.py b/src/TulsiGenerator/Scripts/tulsi_logging.py
index d6cd27a..fccba63 100755
--- a/src/TulsiGenerator/Scripts/tulsi_logging.py
+++ b/src/TulsiGenerator/Scripts/tulsi_logging.py
@@ -35,8 +35,10 @@
     self._logger = logging.getLogger('tulsi_logging')
     self._logger.setLevel(logging.INFO)
 
-    file_handler = logging.handlers.RotatingFileHandler(logfile, backupCount=5)
+    file_handler = logging.handlers.RotatingFileHandler(logfile, backupCount=20)
     file_handler.setLevel(logging.INFO)
+    # Create a new log file for each build.
+    file_handler.doRollover()
     self._logger.addHandler(file_handler)
 
     console = logging.StreamHandler()