Use bash in the Nomulus image (#2959)

/bin/bash comes with the base image, jetty:jdk-??.
Use it in start.sh for safe scripting.

jetty/Dockerfile

@@ -14,4 +14,6 @@ RUN mkdir -p /opt/cprof && \
 USER jetty
 
 EXPOSE 8080
-ENTRYPOINT ["/bin/sh", "/start.sh"]
+# jetty:12-jdk21 has bash. We can afford the extra 200M in image size over
+# the -alpine flavor.
+ENTRYPOINT ["/bin/bash", "/start.sh"]

jetty/start.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # Copyright 2024 The Nomulus Authors. All Rights Reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");