fix(sdk_lib/make_chroot): make using prebuilt sdk work
fix(sdk_lib/make_chroot): make using prebuilt sdk work

fix a couple of buglets related to using a prebuilt sdk chroot

bcwaldon/coreos-scripts,nicescale/scripts,mjg59/scripts,mischief/scripts,endocode/scripts,endocode/scripts,BugRoger/scripts,marineam/coreos-scripts,trnubo/scripts,gtank/scripts,sigma/coreos-scripts,zhang0137/scripts,crawford/scripts,nicescale/scripts,vmware/coreos-scripts,coreos/scripts,fivethreeo/scripts,fivethreeo/scripts,vmware/coreos-scripts,andrejro/coreos--scripts,marineam/coreos-scripts,zhang0137/scripts,glevand/coreos--scripts,endocode/scripts,trnubo/scripts,mjg59/scripts,BugRoger/scripts,andrejro/coreos--scripts,sigma/coreos-scripts,bcwaldon/coreos-scripts,gtank/scripts,coreos/scripts,mischief/scripts,zhang0137/scripts,mischief/scripts,marineam/coreos-scripts,smilart/scripts,nicescale/scripts,crawford/scripts,gtank/scripts,glevand/coreos--scripts,sigma/coreos-scripts,smilart/scripts,smilart/scripts,vmware/coreos-scripts,BugRoger/scripts,mjg59/scripts,bcwaldon/coreos-scripts,crawford/scripts,trnubo/scripts,andrejro/coreos--scripts,fivethreeo/scripts