Update build.sh

Moved the #!/bin/bash on first line, otherwise the script won't run
diff --git a/docker/maven-build/files/build.sh b/docker/maven-build/files/build.sh
index 600752e..b86fc91 100755
--- a/docker/maven-build/files/build.sh
+++ b/docker/maven-build/files/build.sh
@@ -1,3 +1,4 @@
+#!/bin/bash
 #
 #   Licensed to the Apache Software Foundation (ASF) under one 
 #   or more contributor license agreements.  See the NOTICE file
@@ -16,7 +17,6 @@
 #   specific language governing permissions and limitations
 #   under the License.
 #
-#!/bin/bash
 
 # Stop execution if any command fails (i.e. exits with status code > 0)
 set -e