Adding Checkstyle daemon

Lazily instaniate a checkstyle daemon for the first checkstyle job.
Then, each subsequent checkstyle target uses the daemon.

The daemon is terminated when the parent buck or buckd exits.

Change-Id: I4dbea957f20a3f77048dd25d960b7faa1eafef37
diff --git a/tools/build/conf/pom.xml b/tools/build/conf/pom.xml
index 85c60f7..0d606d2 100644
--- a/tools/build/conf/pom.xml
+++ b/tools/build/conf/pom.xml
@@ -34,5 +34,29 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
 
+    <dependencies>
+        <dependency>
+            <groupId>com.puppycrawl.tools</groupId>
+            <artifactId>checkstyle</artifactId>
+            <version>6.11.2</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <!-- TODO: update once following issue is fixed. -->
+                <!-- https://jira.codehaus.org/browse/MCOMPILER-205 -->
+                <version>2.5.1</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
 </project>