Fix the SConstruct to avoid zipit NameError if zip isn't available.
Fix the SConstruct to avoid zipit NameError if zip isn't available.

timj/scons,andrewyoung1991/scons,andrewyoung1991/scons,andrewyoung1991/scons,timj/scons,timj/scons,timj/scons,Distrotech/scons,timj/scons,timj/scons,timj/scons,Distrotech/scons,andrewyoung1991/scons,andrewyoung1991/scons,Distrotech/scons,Distrotech/scons,timj/scons,timj/scons,Distrotech/scons,andrewyoung1991/scons,andrewyoung1991/scons,andrewyoung1991/scons,andrewyoung1991/scons