How to get the WAS_INSTALL_ROOT?

I need to include the com.ibm.ws.ejb.thinclient_7.0.0.jar but right now I hard-coded the path

compile fileTree(dir: “C:/IBMRAD8/runtimes/base_v7/runtimes/”, include: [
‘com.ibm.ws.ejb.thinclient_7.0.0.jar’
])

C:/IBMRAD8/runtimes/base_v7 is my WAS_INSTALL_ROOT. I tried System.getenv(‘WAS_INSTALL_ROOT’) but I got null. Is there a way to get the WAS_INSTALL_ROOT in gradle or maybe a better way to include the com.ibm.ws.ejb.thinclient jar?

If you open a Windows prompt and type echo %WAS_INSTALL_ROOT%, what do you get ?