make testSDKMustBeValid pass.
make testSDKMustBeValid pass.

It wasn't using faked xcodebuild output when calling
GetAvailableSDKsAndAliases(), and so it would sometimes fail if you
didn't have the right SDKs installed locally.

jspahrsummers/xctool,leopardpan/xctool,theiren46/xctool,bhamiltoncx/xctool,soundcloud/xctool,leopardpan/xctool,ACChe/xctool,yaoxiaoyong/xctool,soundcloud/xctool,facebook/xctool,bhamiltoncx/xctool,theiren46/xctool,n054/xctool,leopardpan/xctool,soundcloud/xctool,1yvT0s/xctool,kernandreas/xctool,lqi/xctool,LegNeato/xctool,agreco/xctool,soundcloud/xctool,bhamiltoncx/xctool,FiftyThree/xctool,kernandreas/xctool,SuPair/xctool,1yvT0s/xctool,bhamiltoncx/xctool,FiftyThree/xctool,kamoljan/xctool,jspahrsummers/xctool,ACChe/xctool,ACChe/xctool,duk42111/xctool,kamoljan/xctool,blighli/xctool,1yvT0s/xctool,Richardlihui/xctool,agreco/xctool,yaoxiaoyong/xctool,AutoScout24/xctool,modulexcite/xctool,githubdelegate/xctool,adamjernst/xctool,ACChe/xctool,1yvT0s/xctool,dvor/xctool,facebook/xctool,trello/xctool,agreco/xctool,lpios/xctool,PSPDFKit-labs/xctool,AutoScout24/xctool,trello/xctool,lqi/xctool,kernandreas/xctool,SuPair/xctool,PSPDFKit-labs/xctool,soundcloud/xctool,AutoScout24/xctool,bgertzfield/xctool,bgertzfield/xctool,n054/xctool,kcoons/xctool,lqi/xctool,facebook/xctool,leopardpan/xctool,adamjernst/xctool,dvor/xctool,n054/xctool,kcoons/xctool,bgertzfield/xctool,lpios/xctool,githubdelegate/xctool,adamjernst/xctool,jspahrsummers/xctool,githubdelegate/xctool,ACChe/xctool,bgertzfield/xctool,AutoScout24/xctool,bhamiltoncx/xctool,n054/xctool,lpios/xctool,dvor/xctool,bhamiltoncx/xctool,yaoxiaoyong/xctool,Monits/xctool,ekingo/xctool,kernandreas/xctool,ekingo/xctool,Monits/xctool,FiftyThree/xctool,blighli/xctool,lpios/xctool,Richardlihui/xctool,yaoxiaoyong/xctool,Monits/xctool,SuPair/xctool,PSPDFKit-labs/xctool,lpios/xctool,ekingo/xctool,duk42111/xctool,Monits/xctool,LegNeato/xctool,PSPDFKit-labs/xctool,kamoljan/xctool,lpios/xctool,facebook/xctool,kcoons/xctool,n054/xctool,modulexcite/xctool,Richardlihui/xctool,modulexcite/xctool,jspahrsummers/xctool,duk42111/xctool,facebook/xctool,trello/xctool,blighli/xctool,FiftyThree/xctool,soundcloud/xctool,theiren46/xctool,Richardlihui/xctool,facebook/xctool,blighli/xctool,agreco/xctool,SuPair/xctool,bgertzfield/xctool,adamjernst/xctool,trello/xctool,dvor/xctool,bgertzfield/xctool,kamoljan/xctool,ekingo/xctool,n054/xctool,modulexcite/xctool,LegNeato/xctool,duk42111/xctool,githubdelegate/xctool,ACChe/xctool,theiren46/xctool,LegNeato/xctool,PSPDFKit-labs/xctool