Error out on invalid LLDB build configurations on OS X.
Error out on invalid LLDB build configurations on OS X.

https://bugs.swift.org/browse/SR-18

deyton/swift,kstaring/swift,aschwaighofer/swift,CodaFi/swift,apple/swift,jtbandes/swift,bitjammer/swift,austinzheng/swift,hooman/swift,calebd/swift,russbishop/swift,milseman/swift,IngmarStein/swift,hughbe/swift,hughbe/swift,brentdax/swift,cbrentharris/swift,SwiftAndroid/swift,danielmartin/swift,LeoShimonaka/swift,return/swift,kentya6/swift,JaSpa/swift,Jnosh/swift,dduan/swift,sschiau/swift,russbishop/swift,gottesmm/swift,devincoughlin/swift,gregomni/swift,milseman/swift,apple/swift,gregomni/swift,glessard/swift,kstaring/swift,parkera/swift,xwu/swift,KrishMunot/swift,swiftix/swift,kusl/swift,adrfer/swift,manavgabhawala/swift,alblue/swift,xedin/swift,tardieu/swift,brentdax/swift,devincoughlin/swift,jtbandes/swift,manavgabhawala/swift,kperryua/swift,benlangmuir/swift,calebd/swift,jckarter/swift,zisko/swift,kentya6/swift,devincoughlin/swift,adrfer/swift,harlanhaskins/swift,frootloops/swift,Jnosh/swift,JaSpa/swift,atrick/swift,frootloops/swift,jckarter/swift,uasys/swift,karwa/swift,ken0nek/swift,kstaring/swift,IngmarStein/swift,bitjammer/swift,huonw/swift,bitjammer/swift,tkremenek/swift,practicalswift/swift,calebd/swift,austinzheng/swift,sschiau/swift,kperryua/swift,jckarter/swift,jtbandes/swift,sschiau/swift,amraboelela/swift,IngmarStein/swift,return/swift,brentdax/swift,glessard/swift,huonw/swift,manavgabhawala/swift,atrick/swift,shajrawi/swift,felix91gr/swift,khizkhiz/swift,jopamer/swift,karwa/swift,natecook1000/swift,calebd/swift,rudkx/swift,bitjammer/swift,karwa/swift,allevato/swift,Jnosh/swift,gregomni/swift,brentdax/swift,tardieu/swift,huonw/swift,xwu/swift,swiftix/swift,hooman/swift,glessard/swift,parkera/swift,frootloops/swift,milseman/swift,kentya6/swift,SwiftAndroid/swift,parkera/swift,ahoppen/swift,jopamer/swift,djwbrown/swift,karwa/swift,gribozavr/swift,aschwaighofer/swift,bitjammer/swift,kstaring/swift,emilstahl/swift,mightydeveloper/swift,stephentyrone/swift,arvedviehweger/swift,shahmishal/swift,devincoughlin/swift,glessard/swift,kentya6/swift,natecook1000/swift,IngmarStein/swift,SwiftAndroid/swift,xedin/swift,lorentey/swift,tkremenek/swift,jopamer/swift,tardieu/swift,austinzheng/swift,frootloops/swift,tjw/swift,cbrentharris/swift,shajrawi/swift,gribozavr/swift,harlanhaskins/swift,jmgc/swift,shahmishal/swift,danielmartin/swift,ahoppen/swift,bitjammer/swift,dreamsxin/swift,felix91gr/swift,xwu/swift,LeoShimonaka/swift,xedin/swift,danielmartin/swift,shajrawi/swift,LeoShimonaka/swift,shajrawi/swift,roambotics/swift,gmilos/swift,felix91gr/swift,CodaFi/swift,khizkhiz/swift,devincoughlin/swift,jmgc/swift,ken0nek/swift,slavapestov/swift,roambotics/swift,SwiftAndroid/swift,ken0nek/swift,adrfer/swift,gribozavr/swift,swiftix/swift,hooman/swift,tkremenek/swift,shahmishal/swift,ben-ng/swift,return/swift,therealbnut/swift,johnno1962d/swift,modocache/swift,modocache/swift,cbrentharris/swift,SwiftAndroid/swift,JGiola/swift,hooman/swift,slavapestov/swift,ahoppen/swift,mightydeveloper/swift,kperryua/swift,hughbe/swift,glessard/swift,russbishop/swift,aschwaighofer/swift,JGiola/swift,danielmartin/swift,CodaFi/swift,slavapestov/swift,practicalswift/swift,zisko/swift,felix91gr/swift,uasys/swift,swiftix/swift,lorentey/swift,mightydeveloper/swift,shajrawi/swift,alblue/swift,emilstahl/swift,djwbrown/swift,modocache/swift,therealbnut/swift,devincoughlin/swift,tinysun212/swift-windows,emilstahl/swift,OscarSwanros/swift,manavgabhawala/swift,return/swift,brentdax/swift,adrfer/swift,natecook1000/swift,djwbrown/swift,nathawes/swift,johnno1962d/swift,kentya6/swift,Jnosh/swift,rudkx/swift,stephentyrone/swift,frootloops/swift,CodaFi/swift,arvedviehweger/swift,arvedviehweger/swift,benlangmuir/swift,calebd/swift,return/swift,parkera/swift,CodaFi/swift,practicalswift/swift,practicalswift/swift,danielmartin/swift,gregomni/swift,LeoShimonaka/swift,JaSpa/swift,djwbrown/swift,parkera/swift,LeoShimonaka/swift,austinzheng/swift,kstaring/swift,benlangmuir/swift,huonw/swift,hughbe/swift,tinysun212/swift-windows,lorentey/swift,benlangmuir/swift,ben-ng/swift,allevato/swift,milseman/swift,KrishMunot/swift,jckarter/swift,tkremenek/swift,harlanhaskins/swift,russbishop/swift,harlanhaskins/swift,atrick/swift,MukeshKumarS/Swift,codestergit/swift,amraboelela/swift,roambotics/swift,djwbrown/swift,khizkhiz/swift,airspeedswift/swift,slavapestov/swift,gribozavr/swift,emilstahl/swift,glessard/swift,Jnosh/swift,rudkx/swift,modocache/swift,dduan/swift,gmilos/swift,bitjammer/swift,gribozavr/swift,JGiola/swift,deyton/swift,adrfer/swift,austinzheng/swift,emilstahl/swift,tinysun212/swift-windows,xedin/swift,allevato/swift,felix91gr/swift,therealbnut/swift,zisko/swift,swiftix/swift,kstaring/swift,gmilos/swift,uasys/swift,jmgc/swift,tardieu/swift,mightydeveloper/swift,danielmartin/swift,kperryua/swift,khizkhiz/swift,Jnosh/swift,return/swift,johnno1962d/swift,cbrentharris/swift,practicalswift/swift,zisko/swift,stephentyrone/swift,milseman/swift,kperryua/swift,OscarSwanros/swift,nathawes/swift,apple/swift,harlanhaskins/swift,CodaFi/swift,JaSpa/swift,aschwaighofer/swift,arvedviehweger/swift,aschwaighofer/swift,stephentyrone/swift,LeoShimonaka/swift,benlangmuir/swift,codestergit/swift,karwa/swift,tkremenek/swift,devincoughlin/swift,gribozavr/swift,hooman/swift,therealbnut/swift,cbrentharris/swift,codestergit/swift,calebd/swift,JGiola/swift,tjw/swift,jckarter/swift,shahmishal/swift,IngmarStein/swift,gottesmm/swift,jmgc/swift,kusl/swift,kusl/swift,manavgabhawala/swift,johnno1962d/swift,sschiau/swift,austinzheng/swift,alblue/swift,OscarSwanros/swift,dduan/swift,aschwaighofer/swift,russbishop/swift,therealbnut/swift,brentdax/swift,LeoShimonaka/swift,deyton/swift,xedin/swift,alblue/swift,shajrawi/swift,dreamsxin/swift,hughbe/swift,SwiftAndroid/swift,jckarter/swift,slavapestov/swift,cbrentharris/swift,return/swift,russbishop/swift,roambotics/swift,JaSpa/swift,gottesmm/swift,rudkx/swift,shajrawi/swift,karwa/swift,kusl/swift,jmgc/swift,felix91gr/swift,gmilos/swift,dduan/swift,jtbandes/swift,emilstahl/swift,kperryua/swift,JaSpa/swift,huonw/swift,johnno1962d/swift,LeoShimonaka/swift,milseman/swift,airspeedswift/swift,roambotics/swift,atrick/swift,devincoughlin/swift,gregomni/swift,sschiau/swift,milseman/swift,modocache/swift,alblue/swift,mightydeveloper/swift,modocache/swift,lorentey/swift,khizkhiz/swift,deyton/swift,ben-ng/swift,djwbrown/swift,tinysun212/swift-windows,allevato/swift,CodaFi/swift,shahmishal/swift,mightydeveloper/swift,kperryua/swift,sschiau/swift,practicalswift/swift,uasys/swift,cbrentharris/swift,apple/swift,swiftix/swift,zisko/swift,arvedviehweger/swift,codestergit/swift,harlanhaskins/swift,MukeshKumarS/Swift,rudkx/swift,practicalswift/swift,jtbandes/swift,rudkx/swift,tjw/swift,MukeshKumarS/Swift,ben-ng/swift,stephentyrone/swift,uasys/swift,xwu/swift,nathawes/swift,tinysun212/swift-windows,KrishMunot/swift,adrfer/swift,natecook1000/swift,KrishMunot/swift,arvedviehweger/swift,benlangmuir/swift,khizkhiz/swift,MukeshKumarS/Swift,ben-ng/swift,frootloops/swift,allevato/swift,parkera/swift,shahmishal/swift,OscarSwanros/swift,amraboelela/swift,codestergit/swift,amraboelela/swift,IngmarStein/swift,nathawes/swift,shahmishal/swift,atrick/swift,adrfer/swift,OscarSwanros/swift,IngmarStein/swift,manavgabhawala/swift,hughbe/swift,tkremenek/swift,tinysun212/swift-windows,jtbandes/swift,sschiau/swift,jtbandes/swift,tardieu/swift,KrishMunot/swift,xedin/swift,codestergit/swift,MukeshKumarS/Swift,sschiau/swift,jopamer/swift,tjw/swift,kusl/swift,calebd/swift,natecook1000/swift,emilstahl/swift,zisko/swift,MukeshKumarS/Swift,tjw/swift,gmilos/swift,gottesmm/swift,xwu/swift,felix91gr/swift,jckarter/swift,gregomni/swift,stephentyrone/swift,parkera/swift,apple/swift,karwa/swift,airspeedswift/swift,tardieu/swift,tardieu/swift,kentya6/swift,therealbnut/swift,tkremenek/swift,kentya6/swift,nathawes/swift,hooman/swift,slavapestov/swift,xedin/swift,shahmishal/swift,Jnosh/swift,dduan/swift,dduan/swift,huonw/swift,deyton/swift,zisko/swift,xwu/swift,allevato/swift,johnno1962d/swift,shajrawi/swift,mightydeveloper/swift,gottesmm/swift,stephentyrone/swift,uasys/swift,cbrentharris/swift,parkera/swift,manavgabhawala/swift,jopamer/swift,alblue/swift,airspeedswift/swift,ken0nek/swift,harlanhaskins/swift,natecook1000/swift,modocache/swift,JGiola/swift,kusl/swift,ken0nek/swift,amraboelela/swift,MukeshKumarS/Swift,tinysun212/swift-windows,JaSpa/swift,nathawes/swift,khizkhiz/swift,jopamer/swift,amraboelela/swift,gribozavr/swift,codestergit/swift,ahoppen/swift,emilstahl/swift,lorentey/swift,hooman/swift,ken0nek/swift,OscarSwanros/swift,gmilos/swift,kusl/swift,ben-ng/swift,xwu/swift,amraboelela/swift,deyton/swift,gottesmm/swift,slavapestov/swift,russbishop/swift,jmgc/swift,deyton/swift,gmilos/swift,natecook1000/swift,kstaring/swift,lorentey/swift,roambotics/swift,therealbnut/swift,airspeedswift/swift,johnno1962d/swift,lorentey/swift,djwbrown/swift,huonw/swift,tjw/swift,arvedviehweger/swift,ben-ng/swift,allevato/swift,dduan/swift,tjw/swift,mightydeveloper/swift,airspeedswift/swift,KrishMunot/swift,jmgc/swift,OscarSwanros/swift,kentya6/swift,gribozavr/swift,aschwaighofer/swift,danielmartin/swift,practicalswift/swift,swiftix/swift,apple/swift,karwa/swift,ahoppen/swift,atrick/swift,nathawes/swift,JGiola/swift,jopamer/swift,alblue/swift,hughbe/swift,ahoppen/swift,KrishMunot/swift,frootloops/swift,xedin/swift,ken0nek/swift,kusl/swift,SwiftAndroid/swift,airspeedswift/swift,gottesmm/swift,austinzheng/swift,brentdax/swift,lorentey/swift,uasys/swift