Entropy calculation fails in Docker due to missing 'bc' cmd

In SOLR-16644 the entropy warning in bin/start was modified.

However, when run in default Solr docker image, there is a warning

$ docker run -ti solr:9.4.0 bash
solr@4eacf30312ef:/opt/solr-9.4.0$ bin/solr start -c
Java 17 detected. Enabled workaround for SOLR-16463
bin/solr: line 2408: bc: command not found
Waiting up to 180 seconds to see Solr running on port 8983 [/]  

The script uses a 'bc' command to do the numeric comparison, but that command is not available ootb in our image

Luckily this does not happen when run in foreground, which is the default for the docker image. Thus it is only if you exec into the container and then start solr in the background, which is not very common,