Specify java release to use when building

This is because we see

java.lang.NoSuchMethodError:
java.nio.ByteBuffer.position(I)Ljava/nio/ByteBuffer;

when running on Java 8 when using this in GeoIP2-java, as it gets built
with a newer version of Java apparently.

See jetty/jetty.project#3244.

Do this with a profile because Java 8 does not support the release flag,
which is required for this.

Author: horgh

pom.xml

@@ -130,4 +130,22 @@
         <artifactId>oss-parent</artifactId>
         <version>7</version>
     </parent>
+    <profiles>
+        <profile>
+            <id>active-on-jdk-9-plus</id>
+            <activation>
+                <jdk>[9,)</jdk>
+            </activation>
+            <build>
+                <plugins>
+                    <plugin>
+                        <artifactId>maven-compiler-plugin</artifactId>
+                        <configuration>
+                            <release>8</release>
+                        </configuration>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
 </project>