Add cleanup function to prevent /tmp buildup.

Change-Id: Ia98bb93fab0334410ca17fe9131191a86913389a
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/c/dsg-gnu/Internal/gnu-devtools-for-arm/+/736051


Tested-by: Service account - used by users in DSG GNU team <dgboter@arm.com>
Reviewed-by: Gianluca Busiello <gianluca.busiello@arm.com>