java.lang.ClassNotFoundException: net.rubygrapefruit.platform.Process

I am on windows and trying to build an application which uses a groovy plugin. Inside the groovy plugin, there is an import for net.rubygrapefruit.platform.Process. The import is failing when I run the gradle build with classnotfound exception. I am not sure what’s causing the problem being a gradle novice. From reading the docs, it looks like gradle ships with its own groovy. I found the jar file native-platform-0.10.jar under gradle home.

What else can I check?

gradle -v

Gradle 2.13

Build time: 2016-04-25 04:10:10 UTC
Build number: none
Revision: 3b427b1481e46232107303c90be7b05079b05b1c
Groovy: 2.4.4
Ant: Apache Ant™ version 1.9.6 compiled on June 29 2015
JVM: 1.8.0_92 (Oracle Corporation 25.92-b14)
OS: Windows 7 6.1 x86

Directory of C:\web\gradle\lib

06/05/2016 08:24 PM 61,654 native-platform-0.10.jar
1 File(s) 61,654 bytes

Directory of C:\web\j2016\plugins\gradle\lib

05/14/2016 06:41 AM 61,654 native-platform-0.10.jar
1 File(s) 61,654 bytes

The j2016 is for intellij but I am using the command line gradle for my own install. Gradle_Home is set to c:\web\gradle