make build as reproducible as possible for now

pom.xml

@@ -81,6 +81,7 @@ under the License.
  <properties>
  <javaVersion>7</javaVersion>
  <mavenVersion>3.0</mavenVersion>
+ <project.build.outputTimestamp>2019-12-08T19:56:05Z</project.build.outputTimestamp>
  </properties>
 
  <dependencies>
@@ -155,6 +156,27 @@ under the License.
  </configuration>
  </plugin>
  </plugins>
+ <pluginManagement>
+ <plugins>
+ <!-- Reproducible Builds plugins: to be removed once parent POM updated to 34 -->
+ <plugin>
+ <artifactId>maven-source-plugin</artifactId>
+ <version>3.2.0</version><!-- not fully reproducible: see MSOURCES-123 -->
+ </plugin>
+ <plugin>
+ <artifactId>maven-jar-plugin</artifactId>
+ <version>3.2.0</version>
+ </plugin>
+ <plugin>
+ <artifactId>maven-assembly-plugin</artifactId>
+ <version>3.2.0</version>
+ </plugin>
+ <plugin>
+ <artifactId>maven-release-plugin</artifactId>
+ <version>3.0.0-M1</version>
+ </plugin>
+ </plugins>
+ </pluginManagement>
  </build>
 
  <profiles>