build: remove Swift support for `_add_swift_host_library_single`
build: remove Swift support for `_add_swift_host_library_single`

The host libraries do not build Swift code, these libraries are C++
libraries used for the compiler.

JGiola/swift,CodaFi/swift,tkremenek/swift,atrick/swift,rudkx/swift,glessard/swift,jckarter/swift,jckarter/swift,xwu/swift,harlanhaskins/swift,ahoppen/swift,jmgc/swift,CodaFi/swift,roambotics/swift,glessard/swift,jmgc/swift,airspeedswift/swift,rudkx/swift,allevato/swift,parkera/swift,harlanhaskins/swift,JGiola/swift,hooman/swift,gregomni/swift,atrick/swift,stephentyrone/swift,hooman/swift,CodaFi/swift,glessard/swift,rudkx/swift,jckarter/swift,parkera/swift,tkremenek/swift,hooman/swift,jckarter/swift,allevato/swift,stephentyrone/swift,ahoppen/swift,roambotics/swift,xwu/swift,stephentyrone/swift,apple/swift,atrick/swift,ahoppen/swift,airspeedswift/swift,aschwaighofer/swift,parkera/swift,aschwaighofer/swift,tkremenek/swift,rudkx/swift,tkremenek/swift,jmgc/swift,allevato/swift,CodaFi/swift,allevato/swift,apple/swift,tkremenek/swift,gregomni/swift,airspeedswift/swift,JGiola/swift,aschwaighofer/swift,jmgc/swift,jckarter/swift,jckarter/swift,apple/swift,harlanhaskins/swift,ahoppen/swift,rudkx/swift,gregomni/swift,atrick/swift,nathawes/swift,apple/swift,JGiola/swift,benlangmuir/swift,gregomni/swift,parkera/swift,hooman/swift,roambotics/swift,xwu/swift,benlangmuir/swift,jmgc/swift,aschwaighofer/swift,jmgc/swift,glessard/swift,harlanhaskins/swift,airspeedswift/swift,ahoppen/swift,aschwaighofer/swift,stephentyrone/swift,gregomni/swift,hooman/swift,nathawes/swift,glessard/swift,rudkx/swift,xwu/swift,roambotics/swift,apple/swift,CodaFi/swift,parkera/swift,nathawes/swift,jckarter/swift,airspeedswift/swift,stephentyrone/swift,harlanhaskins/swift,JGiola/swift,jmgc/swift,harlanhaskins/swift,atrick/swift,apple/swift,nathawes/swift,allevato/swift,aschwaighofer/swift,roambotics/swift,tkremenek/swift,airspeedswift/swift,xwu/swift,atrick/swift,benlangmuir/swift,benlangmuir/swift,hooman/swift,benlangmuir/swift,glessard/swift,stephentyrone/swift,parkera/swift,xwu/swift,harlanhaskins/swift,nathawes/swift,allevato/swift,airspeedswift/swift,CodaFi/swift,xwu/swift,parkera/swift,stephentyrone/swift,benlangmuir/swift,parkera/swift,aschwaighofer/swift,gregomni/swift,allevato/swift,roambotics/swift,nathawes/swift,hooman/swift,CodaFi/swift,tkremenek/swift,nathawes/swift,JGiola/swift,ahoppen/swift