build: differentiate better between host and target
build: differentiate better between host and target

Assume that the build currently targets only a single target.  Use the target to
determine the linked libraries for the target library (swiftCore).  This is more
precise and more importantly, is required to enable cross-compilation of various
targets.

harlanhaskins/swift,parkera/swift,lorentey/swift,shahmishal/swift,karwa/swift,jckarter/swift,rudkx/swift,benlangmuir/swift,ahoppen/swift,gregomni/swift,apple/swift,xwu/swift,parkera/swift,austinzheng/swift,nathawes/swift,aschwaighofer/swift,hooman/swift,nathawes/swift,xedin/swift,xedin/swift,devincoughlin/swift,practicalswift/swift,shajrawi/swift,xwu/swift,atrick/swift,practicalswift/swift,shajrawi/swift,nathawes/swift,sschiau/swift,apple/swift,CodaFi/swift,parkera/swift,benlangmuir/swift,aschwaighofer/swift,gregomni/swift,karwa/swift,shahmishal/swift,stephentyrone/swift,aschwaighofer/swift,apple/swift,sschiau/swift,ahoppen/swift,gregomni/swift,gribozavr/swift,austinzheng/swift,shahmishal/swift,jmgc/swift,sschiau/swift,shahmishal/swift,allevato/swift,airspeedswift/swift,gribozavr/swift,sschiau/swift,JGiola/swift,atrick/swift,practicalswift/swift,jckarter/swift,lorentey/swift,devincoughlin/swift,harlanhaskins/swift,tkremenek/swift,roambotics/swift,austinzheng/swift,shajrawi/swift,stephentyrone/swift,jmgc/swift,airspeedswift/swift,jckarter/swift,gribozavr/swift,CodaFi/swift,allevato/swift,amraboelela/swift,lorentey/swift,benlangmuir/swift,gribozavr/swift,austinzheng/swift,shahmishal/swift,JGiola/swift,airspeedswift/swift,rudkx/swift,devincoughlin/swift,JGiola/swift,xwu/swift,stephentyrone/swift,gribozavr/swift,harlanhaskins/swift,xedin/swift,nathawes/swift,stephentyrone/swift,allevato/swift,glessard/swift,jmgc/swift,apple/swift,xwu/swift,CodaFi/swift,jmgc/swift,xedin/swift,benlangmuir/swift,devincoughlin/swift,airspeedswift/swift,shajrawi/swift,gribozavr/swift,glessard/swift,ahoppen/swift,roambotics/swift,jmgc/swift,practicalswift/swift,gribozavr/swift,gregomni/swift,karwa/swift,tkremenek/swift,CodaFi/swift,ahoppen/swift,amraboelela/swift,practicalswift/swift,allevato/swift,karwa/swift,tkremenek/swift,rudkx/swift,parkera/swift,allevato/swift,CodaFi/swift,glessard/swift,roambotics/swift,austinzheng/swift,harlanhaskins/swift,atrick/swift,shajrawi/swift,gribozavr/swift,practicalswift/swift,benlangmuir/swift,amraboelela/swift,shahmishal/swift,harlanhaskins/swift,aschwaighofer/swift,jckarter/swift,rudkx/swift,lorentey/swift,hooman/swift,parkera/swift,stephentyrone/swift,parkera/swift,xedin/swift,airspeedswift/swift,devincoughlin/swift,atrick/swift,aschwaighofer/swift,sschiau/swift,aschwaighofer/swift,devincoughlin/swift,tkremenek/swift,CodaFi/swift,xedin/swift,airspeedswift/swift,shahmishal/swift,harlanhaskins/swift,hooman/swift,xwu/swift,ahoppen/swift,devincoughlin/swift,parkera/swift,lorentey/swift,stephentyrone/swift,practicalswift/swift,xwu/swift,benlangmuir/swift,roambotics/swift,karwa/swift,glessard/swift,nathawes/swift,jckarter/swift,amraboelela/swift,hooman/swift,allevato/swift,shajrawi/swift,stephentyrone/swift,harlanhaskins/swift,glessard/swift,rudkx/swift,hooman/swift,JGiola/swift,tkremenek/swift,rudkx/swift,jmgc/swift,amraboelela/swift,jckarter/swift,atrick/swift,apple/swift,CodaFi/swift,shajrawi/swift,practicalswift/swift,JGiola/swift,JGiola/swift,sschiau/swift,austinzheng/swift,tkremenek/swift,lorentey/swift,sschiau/swift,austinzheng/swift,gregomni/swift,devincoughlin/swift,jckarter/swift,hooman/swift,allevato/swift,apple/swift,roambotics/swift,karwa/swift,xedin/swift,sschiau/swift,amraboelela/swift,xwu/swift,xedin/swift,shahmishal/swift,karwa/swift,aschwaighofer/swift,jmgc/swift,tkremenek/swift,glessard/swift,nathawes/swift,karwa/swift,lorentey/swift,ahoppen/swift,roambotics/swift,lorentey/swift,gregomni/swift,shajrawi/swift,nathawes/swift,parkera/swift,airspeedswift/swift,atrick/swift,amraboelela/swift,hooman/swift