Experimente com o comando env
Exec=/usr/bin/env GTK2_RC_FILES=/home/chris/.gtkrc-eclipse /home/chris/adt-bundle-linux-x86_64-20130522/eclipse/eclipse
Veja man env
NAME
env - run a program in a modified environment
SYNOPSIS
env [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]