Enable using JMH annotation processor on Java>=9

See
- https://issues.apache.org/jira/browse/MCOMPILER-369
- https://stackoverflow.com/questions/53927874/jmh-doesnt-run-inside-a-java-module-unable-to-find-the-resource-meta-inf-ben

Change-Id: Ie810092399d9fe540e5c2e243d3fdb19493c6bcb

org.eclipse.jgit.benchmarks/pom.xml

@@ -95,6 +95,11 @@
             <arg>-J--add-opens=jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED</arg>
           </compilerArgs>
           <annotationProcessorPaths>
+            <path>
+                <groupId>org.openjdk.jmh</groupId>
+                <artifactId>jmh-generator-annprocess</artifactId>
+                <version>${jmh.version}</version>
+            </path>
             <path>
               <groupId>com.google.errorprone</groupId>
               <artifactId>error_prone_core</artifactId>