Add Snapshot maven repository (#941)

* backport PR #829 to 1.x branch, so that we can publish snapshots to our maven repository.
Signed-off-by: Marc Handalian <handalm@amazon.com>

build.gradle

@@ -105,6 +105,14 @@ subprojects {
           name = 'test'
           url = "${rootProject.buildDir}/local-test-repo"
         }
+        maven {
+          name = 'Snapshots'
+          url = 'https://aws.oss.sonatype.org/content/repositories/snapshots'
+          credentials {
+            username "$System.env.SONATYPE_USERNAME"
+            password "$System.env.SONATYPE_PASSWORD"
+          }
+        }
       }
     }
   }