Add hint about late property evaluation in maven-surefire-plugin (#465)

diff --git a/jacoco-maven-plugin/src/org/jacoco/maven/AgentMojo.java b/jacoco-maven-plugin/src/org/jacoco/maven/AgentMojo.java
index 62a92f1..82f59c7 100644
--- a/jacoco-maven-plugin/src/org/jacoco/maven/AgentMojo.java
+++ b/jacoco-maven-plugin/src/org/jacoco/maven/AgentMojo.java
@@ -51,6 +51,11 @@
  * </pre>
  * 
  * <p>
+ * You can define empty property to avoid JVM startup error <code>Could not find or load main class @{argLine}</code>
+ * when using late property evaluation and jacoco-maven-plugin not executed.
+ * </p>
+ * 
+ * <p>
  * Another way is to define "argLine" as a Maven property rather than
  * as part of the configuration of maven-surefire-plugin:
  * </p>