unittests: add stub for `__SwiftValue`
unittests: add stub for `__SwiftValue`

This placeholds the `__SwiftValue` metadata necessary for the Swift
runtime tests.

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