Remove the gem from docker image after installation (#45)

* Add new docker building scripts for logstash

Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>

* Move build related vars to the top

Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>

* Tweak and improve the docker script comments

Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>

* Resolve gem building incorrectly due to move of spec files

Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>

* Remove the gem from docker image after installation

Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>

Author: peterzhuamazon

release/docker/Dockerfile

@@ -16,4 +16,4 @@ FROM docker.elastic.co/logstash/logstash-oss:${VERSION}
 USER logstash
 COPY --chown=logstash:logstash ./logstash-output-opensearch-*.gem /tmp/logstash-output-opensearch.gem
 COPY --chown=logstash:logstash ./logstash-opensearch-sample.conf /usr/share/logstash/config/
-RUN /usr/share/logstash/bin/logstash-plugin install /tmp/logstash-output-opensearch.gem
+RUN /usr/share/logstash/bin/logstash-plugin install /tmp/logstash-output-opensearch.gem && rm -f /tmp/logstash-output-opensearch.gem