run native lib building command from maven

doc/jvm/index.md

@@ -8,6 +8,7 @@ You have find XGBoost JVM Package!
 Installation
 ------------
 To build XGBoost4J contains two steps.
+
 - First type the following command to build JNI library.
 ```bash
 ./create_jni.sh

jvm-packages/xgboost4j/pom.xml

@@ -29,6 +29,22 @@
                     <skipAssembly>false</skipAssembly>
                 </configuration>
             </plugin>
+            <plugin>
+                <artifactId>exec-maven-plugin</artifactId>
+                <groupId>org.codehaus.mojo</groupId>
+                <executions>
+                    <execution><!-- Run our version calculation script -->
+                        <id>native</id>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>exec</goal>
+                        </goals>
+                        <configuration>
+                            <executable>create_jni.sh</executable>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
         </plugins>
     </build>
     <dependencies>

tests/travis/run_test.sh

@@ -75,7 +75,6 @@ if [ ${TASK} == "java_test" ]; then
     set -e
     make jvm-packages
     cd jvm-packages
-    ./create_jni.sh
     mvn clean install -DskipTests=true
     mvn test
 fi