[CMake] Clear the Clang module cache before building the ObjectiveC overlay.
[CMake] Clear the Clang module cache before building the ObjectiveC overlay.

This will catch almost all module cache errors during compiler / stdlib
development, at the cost of slowing down rebuilds of the overlay modules
a bit.

Swift SVN r14364

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