[driver] Pull code generation out into its own function.
[driver] Pull code generation out into its own function.

No functionality change.  Paves the way for generating separate .o
files for each input file.

Swift SVN r9827

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