Move jmh-generator-annprocess dependency to "benchmark" profile

It doesn't seem to like being run again, `mvn clean test && mvn test`
fails with "duplicate class". Moving it to a profile excludes it from
the default build.

Author: robinst

pom.xml

@@ -45,14 +45,22 @@
             <version>1.9.3</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-generator-annprocess</artifactId>
-            <version>1.9.3</version>
-            <scope>test</scope>
-        </dependency>
     </dependencies>
 
+    <profiles>
+        <profile>
+            <id>benchmark</id>
+            <dependencies>
+                <dependency>
+                    <groupId>org.openjdk.jmh</groupId>
+                    <artifactId>jmh-generator-annprocess</artifactId>
+                    <version>1.9.3</version>
+                    <scope>test</scope>
+                </dependency>
+            </dependencies>
+        </profile>
+    </profiles>
+
     <developers>
         <developer>
             <name>Robin Stocker</name>