[AST] Fix a linker error for the parser-only library build
[AST] Fix a linker error for the parser-only library build

Avoids linking LLVMCore library which would not be useful for the parser-only library.

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