Support multi platform Docker build (buildx)

README.md

@@ -31,6 +31,10 @@ To apply your own patches to the Cantaloupe source, create patchfiles with a Git
 
 Patching an older version of Cantaloupe is possible as well.
 
+To use Docker buildkit (builx), supply the list of architectures to build:
+
+    mvn verify -Ddocker.platforms=linux/amd64,linux/arm64
+
 _Hint: If you want to run a build without a Docker cache, add `-Ddocker.noCache` to your mvn command; for instance: `mvn verify -Ddocker.noCache`_
 
 ### Run the Cantaloupe container

pom.xml

@@ -119,6 +119,7 @@
     <docker.cleanup>remove</docker.cleanup>
     <docker.image>cantaloupe${artifact.qualifier}</docker.image>
     <docker.showLogs>true</docker.showLogs>
+    <docker.platforms></docker.platforms>
 
     <!-- We don't need to build the jar outside of the Docker build -->
     <jar.phase></jar.phase>
@@ -394,6 +395,12 @@
                   <name>${docker.image}</name>
                   <build>
                     <dockerFile>${project.basedir}/src/main/docker/Dockerfile</dockerFile>
+                    <buildx>
+                      <platforms>
+                        <!-- set comma separated list of platforms in ${docker.platforms} to invoke buildkit -->
+                        <platform>${docker.platforms}</platform>
+                      </platforms>
+                    </buildx>
                   </build>
                   <run>
                     <ports>