Add ppc64le support on travis-ci

* Add ppc64le arch

* Download mvn 3.6.3 binary for ppc64le

To remove build failure due to lower maven version(3.3.9) on xenial pcc64le

.travis.yml

@@ -1,2 +1,11 @@
 language: java
+jobs:
+  include:
+    - arch: amd64
+    - arch: ppc64le
+      before_install: 
+        - mkdir -p /opt/maven
+        - curl https://downloads.apache.org/maven/maven-3/3.6.3/binaries/apache-maven-3.6.3-bin.tar.gz|tar -xz --strip 1 -C /opt/maven
+        - export MAVEN_HOME=/opt/maven
+        - export PATH=${MAVEN_HOME}/bin:${PATH}
 after_failure: print_surefire_reports.sh