[build-script] Adjust how PlaygroundLogger and PlaygroundSupport are built.
[build-script] Adjust how PlaygroundLogger and PlaygroundSupport are built.

Instead of building separately, they are now built together using a new workspace with new schemes.
As a result, xcodebuild is now invoked once per-platform, allowing for platform-specific build setting and architecture overrides.

This addresses <rdar://problem/36512531>.

huonw/swift,parkera/swift,gribozavr/swift,harlanhaskins/swift,harlanhaskins/swift,ahoppen/swift,tkremenek/swift,shahmishal/swift,glessard/swift,gregomni/swift,stephentyrone/swift,apple/swift,jopamer/swift,alblue/swift,allevato/swift,natecook1000/swift,atrick/swift,parkera/swift,airspeedswift/swift,jopamer/swift,rudkx/swift,gribozavr/swift,airspeedswift/swift,CodaFi/swift,stephentyrone/swift,zisko/swift,sschiau/swift,amraboelela/swift,austinzheng/swift,shajrawi/swift,parkera/swift,CodaFi/swift,airspeedswift/swift,roambotics/swift,atrick/swift,jmgc/swift,xedin/swift,brentdax/swift,gregomni/swift,danielmartin/swift,tkremenek/swift,roambotics/swift,practicalswift/swift,jopamer/swift,tkremenek/swift,JGiola/swift,karwa/swift,airspeedswift/swift,zisko/swift,CodaFi/swift,sschiau/swift,roambotics/swift,ahoppen/swift,amraboelela/swift,atrick/swift,sschiau/swift,harlanhaskins/swift,huonw/swift,JGiola/swift,sschiau/swift,CodaFi/swift,hooman/swift,alblue/swift,aschwaighofer/swift,stephentyrone/swift,jmgc/swift,glessard/swift,zisko/swift,devincoughlin/swift,natecook1000/swift,nathawes/swift,nathawes/swift,shajrawi/swift,harlanhaskins/swift,practicalswift/swift,sschiau/swift,atrick/swift,brentdax/swift,danielmartin/swift,practicalswift/swift,gribozavr/swift,airspeedswift/swift,harlanhaskins/swift,aschwaighofer/swift,shajrawi/swift,karwa/swift,practicalswift/swift,alblue/swift,xedin/swift,JGiola/swift,shahmishal/swift,stephentyrone/swift,tkremenek/swift,benlangmuir/swift,xwu/swift,nathawes/swift,lorentey/swift,roambotics/swift,amraboelela/swift,airspeedswift/swift,devincoughlin/swift,zisko/swift,apple/swift,jckarter/swift,practicalswift/swift,gribozavr/swift,tjw/swift,gregomni/swift,allevato/swift,huonw/swift,hooman/swift,shajrawi/swift,tjw/swift,tkremenek/swift,jckarter/swift,austinzheng/swift,shajrawi/swift,lorentey/swift,CodaFi/swift,tjw/swift,benlangmuir/swift,hooman/swift,karwa/swift,sschiau/swift,brentdax/swift,airspeedswift/swift,brentdax/swift,xedin/swift,sschiau/swift,lorentey/swift,natecook1000/swift,karwa/swift,austinzheng/swift,xedin/swift,glessard/swift,allevato/swift,rudkx/swift,shahmishal/swift,nathawes/swift,CodaFi/swift,xwu/swift,xedin/swift,rudkx/swift,glessard/swift,jmgc/swift,atrick/swift,natecook1000/swift,stephentyrone/swift,nathawes/swift,devincoughlin/swift,xwu/swift,shahmishal/swift,nathawes/swift,gregomni/swift,atrick/swift,natecook1000/swift,rudkx/swift,ahoppen/swift,ahoppen/swift,gribozavr/swift,shajrawi/swift,tjw/swift,apple/swift,jckarter/swift,devincoughlin/swift,parkera/swift,aschwaighofer/swift,karwa/swift,practicalswift/swift,xwu/swift,JGiola/swift,amraboelela/swift,brentdax/swift,nathawes/swift,austinzheng/swift,jmgc/swift,danielmartin/swift,huonw/swift,danielmartin/swift,parkera/swift,jopamer/swift,shajrawi/swift,xwu/swift,lorentey/swift,ahoppen/swift,apple/swift,zisko/swift,alblue/swift,jmgc/swift,shahmishal/swift,aschwaighofer/swift,allevato/swift,tjw/swift,lorentey/swift,alblue/swift,brentdax/swift,lorentey/swift,lorentey/swift,xwu/swift,huonw/swift,parkera/swift,parkera/swift,xedin/swift,gregomni/swift,xedin/swift,ahoppen/swift,zisko/swift,karwa/swift,aschwaighofer/swift,karwa/swift,danielmartin/swift,rudkx/swift,hooman/swift,apple/swift,tkremenek/swift,tjw/swift,hooman/swift,practicalswift/swift,parkera/swift,hooman/swift,xedin/swift,zisko/swift,jopamer/swift,jckarter/swift,jckarter/swift,CodaFi/swift,jopamer/swift,xwu/swift,JGiola/swift,brentdax/swift,roambotics/swift,benlangmuir/swift,devincoughlin/swift,amraboelela/swift,jmgc/swift,tkremenek/swift,devincoughlin/swift,benlangmuir/swift,tjw/swift,JGiola/swift,glessard/swift,hooman/swift,amraboelela/swift,stephentyrone/swift,allevato/swift,danielmartin/swift,jmgc/swift,sschiau/swift,amraboelela/swift,shahmishal/swift,devincoughlin/swift,shajrawi/swift,allevato/swift,austinzheng/swift,alblue/swift,alblue/swift,gribozavr/swift,rudkx/swift,harlanhaskins/swift,aschwaighofer/swift,benlangmuir/swift,huonw/swift,huonw/swift,jopamer/swift,jckarter/swift,harlanhaskins/swift,gribozavr/swift,natecook1000/swift,jckarter/swift,austinzheng/swift,glessard/swift,karwa/swift,stephentyrone/swift,aschwaighofer/swift,gregomni/swift,danielmartin/swift,benlangmuir/swift,practicalswift/swift,lorentey/swift,austinzheng/swift,shahmishal/swift,apple/swift,natecook1000/swift,shahmishal/swift,allevato/swift,roambotics/swift,gribozavr/swift,devincoughlin/swift