Update Maven build machinery.

* Require Maven 3.6.3
* Move to antrun plugin 3.0.0
* Move to site plugin 3.9.0
* Move to javadoc plugin 3.2.0

Change-Id: I132e70fc2c751660b3b7e2e54a0d93dc16eb8410
Signed-off-by: Alexander Kurtakov <akurtako@redhat.com>
Reviewed-on: https://git.eclipse.org/r/161510
diff --git a/pom.xml b/pom.xml
index 6dffe0a..668b690 100644
--- a/pom.xml
+++ b/pom.xml
@@ -17,7 +17,7 @@
   <modelVersion>4.0.0</modelVersion>
 
   <prerequisites>
-    <maven>3.3.9</maven>
+    <maven>3.6.3</maven>
   </prerequisites>
   <groupId>org.eclipse.linuxtools</groupId>
   <artifactId>linuxtools-parent</artifactId>
@@ -442,12 +442,12 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-antrun-plugin</artifactId>
-          <version>1.8</version>
+          <version>3.0.0</version>
         </plugin>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-site-plugin</artifactId>
-          <version>3.8.2</version>
+          <version>3.9.0</version>
         </plugin>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
@@ -457,7 +457,7 @@
 	<plugin>
 	  <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-javadoc-plugin</artifactId>
-	  <version>3.1.1</version>
+	  <version>3.2.0</version>
           <configuration>
             <excludePackageNames>org.eclipse.linuxtools.internal.*:*.test*:org.eclipse.linuxtools.docker.reddeer*</excludePackageNames>
           </configuration>