If the DB is in simple recovery, there's absolutely no need to explicitly truncate the logs. That occurs at regular intervals. In simple, the only reason for the log to grow would be faulty replication or long lasting transactions. Index rebuilds fall into the latter.

As for shrinking it, only shrink a log if you know that it won't reach that size again. log grows are expensive and slow the DB down for the duration. Plus repeated shrink/grow causes fragmentation at the file level, which is hard to fix.