stdlib: build multiple platform libraries simultaneously
stdlib: build multiple platform libraries simultaneously

Always construct the platform libraries for all the target SDKs.  This enables
us to build the right set for targets and will also enable us to cross-compile
multiple targets simultaneously.

brentdax/swift,nathawes/swift,hooman/swift,kperryua/swift,swiftix/swift,jmgc/swift,aschwaighofer/swift,bitjammer/swift,apple/swift,parkera/swift,russbishop/swift,karwa/swift,jckarter/swift,CodaFi/swift,calebd/swift,glessard/swift,IngmarStein/swift,gribozavr/swift,airspeedswift/swift,austinzheng/swift,calebd/swift,codestergit/swift,amraboelela/swift,arvedviehweger/swift,jmgc/swift,milseman/swift,roambotics/swift,gribozavr/swift,modocache/swift,gmilos/swift,hughbe/swift,gregomni/swift,bitjammer/swift,jckarter/swift,therealbnut/swift,bitjammer/swift,JGiola/swift,jtbandes/swift,harlanhaskins/swift,djwbrown/swift,jtbandes/swift,devincoughlin/swift,frootloops/swift,gmilos/swift,ben-ng/swift,ben-ng/swift,gmilos/swift,arvedviehweger/swift,djwbrown/swift,return/swift,devincoughlin/swift,deyton/swift,return/swift,swiftix/swift,tinysun212/swift-windows,return/swift,felix91gr/swift,hooman/swift,huonw/swift,natecook1000/swift,atrick/swift,frootloops/swift,zisko/swift,parkera/swift,kperryua/swift,xwu/swift,kperryua/swift,tkremenek/swift,zisko/swift,therealbnut/swift,calebd/swift,tkremenek/swift,JGiola/swift,danielmartin/swift,hooman/swift,parkera/swift,gregomni/swift,shajrawi/swift,sschiau/swift,airspeedswift/swift,swiftix/swift,alblue/swift,shajrawi/swift,practicalswift/swift,gregomni/swift,tkremenek/swift,lorentey/swift,jmgc/swift,tjw/swift,gottesmm/swift,nathawes/swift,xwu/swift,rudkx/swift,modocache/swift,xwu/swift,devincoughlin/swift,manavgabhawala/swift,milseman/swift,uasys/swift,CodaFi/swift,felix91gr/swift,tinysun212/swift-windows,milseman/swift,IngmarStein/swift,amraboelela/swift,djwbrown/swift,parkera/swift,shahmishal/swift,frootloops/swift,jopamer/swift,harlanhaskins/swift,frootloops/swift,karwa/swift,JaSpa/swift,parkera/swift,CodaFi/swift,benlangmuir/swift,practicalswift/swift,atrick/swift,gribozavr/swift,xwu/swift,danielmartin/swift,russbishop/swift,gmilos/swift,jtbandes/swift,stephentyrone/swift,Jnosh/swift,huonw/swift,glessard/swift,xedin/swift,CodaFi/swift,codestergit/swift,xedin/swift,OscarSwanros/swift,milseman/swift,lorentey/swift,codestergit/swift,shajrawi/swift,xedin/swift,tjw/swift,xedin/swift,xedin/swift,practicalswift/swift,russbishop/swift,djwbrown/swift,gribozavr/swift,allevato/swift,milseman/swift,parkera/swift,JaSpa/swift,ahoppen/swift,rudkx/swift,tjw/swift,xedin/swift,JaSpa/swift,russbishop/swift,hooman/swift,arvedviehweger/swift,manavgabhawala/swift,therealbnut/swift,IngmarStein/swift,practicalswift/swift,stephentyrone/swift,shahmishal/swift,huonw/swift,ben-ng/swift,hooman/swift,airspeedswift/swift,xwu/swift,bitjammer/swift,tardieu/swift,atrick/swift,JGiola/swift,airspeedswift/swift,natecook1000/swift,brentdax/swift,tinysun212/swift-windows,jtbandes/swift,gregomni/swift,gribozavr/swift,manavgabhawala/swift,zisko/swift,milseman/swift,deyton/swift,aschwaighofer/swift,natecook1000/swift,allevato/swift,amraboelela/swift,rudkx/swift,tardieu/swift,allevato/swift,Jnosh/swift,alblue/swift,hughbe/swift,felix91gr/swift,kstaring/swift,jtbandes/swift,hughbe/swift,rudkx/swift,shahmishal/swift,shahmishal/swift,IngmarStein/swift,shahmishal/swift,jopamer/swift,aschwaighofer/swift,modocache/swift,gmilos/swift,tinysun212/swift-windows,benlangmuir/swift,manavgabhawala/swift,IngmarStein/swift,jmgc/swift,roambotics/swift,gregomni/swift,apple/swift,atrick/swift,apple/swift,jopamer/swift,amraboelela/swift,glessard/swift,austinzheng/swift,OscarSwanros/swift,swiftix/swift,lorentey/swift,Jnosh/swift,danielmartin/swift,karwa/swift,russbishop/swift,Jnosh/swift,felix91gr/swift,frootloops/swift,tkremenek/swift,xedin/swift,gottesmm/swift,nathawes/swift,benlangmuir/swift,hughbe/swift,bitjammer/swift,practicalswift/swift,modocache/swift,OscarSwanros/swift,bitjammer/swift,uasys/swift,jopamer/swift,gottesmm/swift,modocache/swift,lorentey/swift,kstaring/swift,deyton/swift,allevato/swift,allevato/swift,return/swift,zisko/swift,harlanhaskins/swift,amraboelela/swift,danielmartin/swift,sschiau/swift,stephentyrone/swift,hooman/swift,zisko/swift,karwa/swift,arvedviehweger/swift,deyton/swift,kstaring/swift,devincoughlin/swift,jckarter/swift,tardieu/swift,sschiau/swift,natecook1000/swift,russbishop/swift,rudkx/swift,tjw/swift,manavgabhawala/swift,zisko/swift,aschwaighofer/swift,brentdax/swift,uasys/swift,roambotics/swift,calebd/swift,ben-ng/swift,ben-ng/swift,xwu/swift,jckarter/swift,lorentey/swift,devincoughlin/swift,kperryua/swift,ahoppen/swift,alblue/swift,devincoughlin/swift,hughbe/swift,harlanhaskins/swift,huonw/swift,austinzheng/swift,IngmarStein/swift,swiftix/swift,sschiau/swift,gottesmm/swift,apple/swift,CodaFi/swift,sschiau/swift,frootloops/swift,karwa/swift,return/swift,alblue/swift,manavgabhawala/swift,return/swift,swiftix/swift,glessard/swift,nathawes/swift,kperryua/swift,practicalswift/swift,lorentey/swift,OscarSwanros/swift,hughbe/swift,ahoppen/swift,hughbe/swift,danielmartin/swift,shajrawi/swift,alblue/swift,parkera/swift,austinzheng/swift,ben-ng/swift,lorentey/swift,karwa/swift,huonw/swift,codestergit/swift,codestergit/swift,airspeedswift/swift,calebd/swift,tardieu/swift,sschiau/swift,kstaring/swift,austinzheng/swift,jopamer/swift,ahoppen/swift,karwa/swift,therealbnut/swift,arvedviehweger/swift,roambotics/swift,tinysun212/swift-windows,uasys/swift,shajrawi/swift,tardieu/swift,aschwaighofer/swift,OscarSwanros/swift,codestergit/swift,ahoppen/swift,huonw/swift,shahmishal/swift,jtbandes/swift,gottesmm/swift,amraboelela/swift,natecook1000/swift,apple/swift,rudkx/swift,austinzheng/swift,benlangmuir/swift,amraboelela/swift,swiftix/swift,CodaFi/swift,allevato/swift,CodaFi/swift,aschwaighofer/swift,devincoughlin/swift,benlangmuir/swift,tardieu/swift,uasys/swift,brentdax/swift,jckarter/swift,harlanhaskins/swift,kperryua/swift,harlanhaskins/swift,tinysun212/swift-windows,Jnosh/swift,JaSpa/swift,uasys/swift,natecook1000/swift,gmilos/swift,nathawes/swift,codestergit/swift,danielmartin/swift,harlanhaskins/swift,calebd/swift,brentdax/swift,brentdax/swift,JGiola/swift,JaSpa/swift,felix91gr/swift,stephentyrone/swift,nathawes/swift,practicalswift/swift,alblue/swift,xedin/swift,milseman/swift,kstaring/swift,Jnosh/swift,glessard/swift,parkera/swift,therealbnut/swift,deyton/swift,OscarSwanros/swift,JaSpa/swift,danielmartin/swift,arvedviehweger/swift,deyton/swift,airspeedswift/swift,shajrawi/swift,gottesmm/swift,kstaring/swift,karwa/swift,JGiola/swift,therealbnut/swift,airspeedswift/swift,ahoppen/swift,tardieu/swift,uasys/swift,austinzheng/swift,modocache/swift,shahmishal/swift,glessard/swift,huonw/swift,benlangmuir/swift,felix91gr/swift,gribozavr/swift,sschiau/swift,calebd/swift,JaSpa/swift,tjw/swift,shahmishal/swift,atrick/swift,djwbrown/swift,manavgabhawala/swift,IngmarStein/swift,tjw/swift,kstaring/swift,deyton/swift,tjw/swift,OscarSwanros/swift,devincoughlin/swift,stephentyrone/swift,jopamer/swift,brentdax/swift,jtbandes/swift,modocache/swift,arvedviehweger/swift,zisko/swift,jmgc/swift,natecook1000/swift,jmgc/swift,djwbrown/swift,therealbnut/swift,bitjammer/swift,practicalswift/swift,stephentyrone/swift,alblue/swift,tkremenek/swift,tkremenek/swift,tkremenek/swift,xwu/swift,gottesmm/swift,shajrawi/swift,kperryua/swift,gregomni/swift,apple/swift,roambotics/swift,sschiau/swift,russbishop/swift,jopamer/swift,atrick/swift,hooman/swift,felix91gr/swift,JGiola/swift,gribozavr/swift,Jnosh/swift,jckarter/swift,shajrawi/swift,gribozavr/swift,stephentyrone/swift,return/swift,allevato/swift,djwbrown/swift,lorentey/swift,roambotics/swift,nathawes/swift,jckarter/swift,frootloops/swift,aschwaighofer/swift,tinysun212/swift-windows,jmgc/swift,gmilos/swift,ben-ng/swift