Fix warning in build: [WARNING] bad path element "": no such file or directory

Release Notes - Maven 2.x Compiler Plugin - Version 3.0

** Bug
    * [MCOMPILER-160] - javac error but build SUCCESS
    * [MCOMPILER-173] - use new maven plugin annotations
    * [MCOMPILER-179] - Warnings
    * [MCOMPILER-181] - Exception on compilation are not properly reported
    * [MCOMPILER-182] - Case sensitivity changes in class names not
detected by compiler
    * [MCOMPILER-184] - use last plexus-compiler 2.0 api
    * [MCOMPILER-186] - mojos are in wrong package (org.apache.maven.plugin)

** Task
    * [MCOMPILER-171] - use maven-plugin-tools' java 5 annotations