[build-script] copy over the compiler-rt .a archives from the toolchian only when necessary
[build-script] copy over the compiler-rt .a archives from the toolchian only when necessary

parkera/swift,apple/swift,tkremenek/swift,hooman/swift,JGiola/swift,roambotics/swift,rudkx/swift,roambotics/swift,atrick/swift,JGiola/swift,hooman/swift,jmgc/swift,JGiola/swift,gregomni/swift,atrick/swift,atrick/swift,jmgc/swift,xwu/swift,apple/swift,JGiola/swift,rudkx/swift,benlangmuir/swift,xwu/swift,parkera/swift,roambotics/swift,ahoppen/swift,ahoppen/swift,ahoppen/swift,rudkx/swift,JGiola/swift,JGiola/swift,apple/swift,apple/swift,ahoppen/swift,ahoppen/swift,roambotics/swift,roambotics/swift,glessard/swift,xwu/swift,glessard/swift,xwu/swift,glessard/swift,gregomni/swift,xwu/swift,tkremenek/swift,hooman/swift,gregomni/swift,jmgc/swift,parkera/swift,benlangmuir/swift,rudkx/swift,hooman/swift,xwu/swift,hooman/swift,gregomni/swift,benlangmuir/swift,ahoppen/swift,jmgc/swift,jmgc/swift,glessard/swift,gregomni/swift,hooman/swift,roambotics/swift,apple/swift,jmgc/swift,tkremenek/swift,parkera/swift,rudkx/swift,hooman/swift,rudkx/swift,glessard/swift,parkera/swift,xwu/swift,jmgc/swift,tkremenek/swift,parkera/swift,atrick/swift,benlangmuir/swift,benlangmuir/swift,atrick/swift,parkera/swift,parkera/swift,tkremenek/swift,benlangmuir/swift,glessard/swift,gregomni/swift,tkremenek/swift,tkremenek/swift,atrick/swift,apple/swift