[build-script] Push build-swift-stdlib-unittest-extra one level down
[build-script] Push build-swift-stdlib-unittest-extra one level down

This will allow us to disable building StdlibUnittest for
specific presets.

CodaFi/swift,gribozavr/swift,glessard/swift,atrick/swift,nathawes/swift,rudkx/swift,parkera/swift,xwu/swift,benlangmuir/swift,apple/swift,karwa/swift,xwu/swift,stephentyrone/swift,gribozavr/swift,gribozavr/swift,airspeedswift/swift,karwa/swift,gribozavr/swift,glessard/swift,tkremenek/swift,parkera/swift,gregomni/swift,karwa/swift,lorentey/swift,gregomni/swift,parkera/swift,rudkx/swift,atrick/swift,airspeedswift/swift,aschwaighofer/swift,lorentey/swift,hooman/swift,lorentey/swift,rudkx/swift,tkremenek/swift,tkremenek/swift,jckarter/swift,JGiola/swift,tkremenek/swift,hooman/swift,JGiola/swift,nathawes/swift,stephentyrone/swift,roambotics/swift,gribozavr/swift,stephentyrone/swift,jmgc/swift,roambotics/swift,roambotics/swift,jckarter/swift,lorentey/swift,aschwaighofer/swift,karwa/swift,xwu/swift,allevato/swift,hooman/swift,allevato/swift,airspeedswift/swift,harlanhaskins/swift,gregomni/swift,benlangmuir/swift,harlanhaskins/swift,gribozavr/swift,hooman/swift,ahoppen/swift,jckarter/swift,ahoppen/swift,jckarter/swift,allevato/swift,xwu/swift,CodaFi/swift,jmgc/swift,jckarter/swift,jmgc/swift,nathawes/swift,hooman/swift,CodaFi/swift,harlanhaskins/swift,gregomni/swift,apple/swift,karwa/swift,ahoppen/swift,roambotics/swift,benlangmuir/swift,xwu/swift,jmgc/swift,nathawes/swift,jckarter/swift,roambotics/swift,rudkx/swift,JGiola/swift,CodaFi/swift,lorentey/swift,gregomni/swift,lorentey/swift,aschwaighofer/swift,allevato/swift,jckarter/swift,xwu/swift,rudkx/swift,karwa/swift,gribozavr/swift,CodaFi/swift,glessard/swift,atrick/swift,airspeedswift/swift,JGiola/swift,aschwaighofer/swift,atrick/swift,hooman/swift,allevato/swift,JGiola/swift,parkera/swift,allevato/swift,harlanhaskins/swift,gregomni/swift,stephentyrone/swift,xwu/swift,gribozavr/swift,roambotics/swift,rudkx/swift,aschwaighofer/swift,karwa/swift,ahoppen/swift,airspeedswift/swift,stephentyrone/swift,nathawes/swift,lorentey/swift,apple/swift,parkera/swift,aschwaighofer/swift,harlanhaskins/swift,tkremenek/swift,allevato/swift,benlangmuir/swift,nathawes/swift,glessard/swift,parkera/swift,glessard/swift,lorentey/swift,CodaFi/swift,benlangmuir/swift,benlangmuir/swift,hooman/swift,harlanhaskins/swift,airspeedswift/swift,apple/swift,jmgc/swift,nathawes/swift,jmgc/swift,CodaFi/swift,stephentyrone/swift,harlanhaskins/swift,jmgc/swift,atrick/swift,glessard/swift,tkremenek/swift,ahoppen/swift,apple/swift,airspeedswift/swift,apple/swift,parkera/swift,atrick/swift,tkremenek/swift,ahoppen/swift,aschwaighofer/swift,stephentyrone/swift,karwa/swift,JGiola/swift,parkera/swift