Set LINUX_GIT in .bashrc for generate-git-snapshot.sh
    
    The script requires  LINUX_GIT to be set, preferably, in your
    local .bashrc. I added a quick check to see if .bashrc exists
    and check it first to see if LINUX_GIT is set there.
    
    [labbott: Tweaked commit text]
    Signed-off-by: Miguel Flores Silverio <floresmigu3l@gmail.com>