Suppress errors for non-ASCII characters in Java files

Change-Id: Iaedc76b640326ee967b7d05937dadce75bb29639
diff --git a/Dockerfile b/Dockerfile
index 6ab7673..acfa707 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -12,6 +12,7 @@
 ENV HOME /root
 ENV JAVA_HOME /usr/lib/jvm/java-8-oracle
 ENV BUILD_NUMBER docker
+ENV JAVA_TOOL_OPTIONS=-Dfile.encoding=UTF8
 
 # Copy in the source
 COPY . /src/onos/