[Docker] Build the jar in Docker since the wrapper now expects it to be there

docker/Dockerfile

@@ -38,12 +38,17 @@ ADD . /tmp/ensembl-hive
 RUN cd /tmp/ensembl-hive && git clean -d -X -f
 RUN rm -rf /tmp/ensembl-hive/.git
 
+# Build the Java wrapper
+FROM maven:3.6-jdk-12-alpine AS java_builder
+COPY --from=repo /tmp/ensembl-hive/wrappers/java /tmp/java_wrapper
+RUN cd /tmp/java_wrapper && mvn package
+
 FROM ubuntu:16.04
 
 # Install some basic utilities
 ARG DEBIAN_FRONTEND=noninteractive
 RUN apt-get update -y \
-    && apt-get install -y maven curl \
+    && apt-get install -y curl \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
@@ -56,6 +61,7 @@ ENV PATH=$JAVA_HOME/bin:$PATH
 
 # Get the repo
 COPY --from=repo /tmp/ensembl-hive /repo/ensembl-hive
+COPY --from=java_builder /tmp/java_wrapper/target/eHive-*-jar-with-dependencies.jar /repo/ensembl-hive/wrappers/java/target/
 
 # Install all the dependencies
 RUN /repo/ensembl-hive/docker/setup_os.Ubuntu-16.04.sh \