[cmake][list] Add utilities to SwiftList.cmake for using cmake lists as sets.
[cmake][list] Add utilities to SwiftList.cmake for using cmake lists as sets.

This will allow for one to work with sets in cmake in a much cleaner
fashion.

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