[build-script] Use --filter to implement --lldb-test-only-swift.
[build-script] Use --filter to implement --lldb-test-only-swift.

<rdar://problem/50211354>

apple/swift,xwu/swift,benlangmuir/swift,rudkx/swift,allevato/swift,tkremenek/swift,allevato/swift,hooman/swift,atrick/swift,aschwaighofer/swift,hooman/swift,hooman/swift,atrick/swift,shajrawi/swift,airspeedswift/swift,xwu/swift,roambotics/swift,atrick/swift,parkera/swift,jckarter/swift,jckarter/swift,benlangmuir/swift,lorentey/swift,apple/swift,stephentyrone/swift,hooman/swift,airspeedswift/swift,shahmishal/swift,lorentey/swift,sschiau/swift,allevato/swift,sschiau/swift,parkera/swift,gribozavr/swift,shajrawi/swift,ahoppen/swift,harlanhaskins/swift,roambotics/swift,apple/swift,ahoppen/swift,glessard/swift,gregomni/swift,nathawes/swift,CodaFi/swift,jmgc/swift,tkremenek/swift,allevato/swift,allevato/swift,airspeedswift/swift,aschwaighofer/swift,nathawes/swift,parkera/swift,JGiola/swift,gribozavr/swift,devincoughlin/swift,shahmishal/swift,tkremenek/swift,jckarter/swift,xedin/swift,jckarter/swift,sschiau/swift,xwu/swift,harlanhaskins/swift,gregomni/swift,parkera/swift,devincoughlin/swift,sschiau/swift,aschwaighofer/swift,tkremenek/swift,JGiola/swift,sschiau/swift,aschwaighofer/swift,karwa/swift,jmgc/swift,JGiola/swift,parkera/swift,xedin/swift,rudkx/swift,jmgc/swift,karwa/swift,atrick/swift,allevato/swift,CodaFi/swift,jckarter/swift,apple/swift,ahoppen/swift,nathawes/swift,harlanhaskins/swift,sschiau/swift,CodaFi/swift,gribozavr/swift,devincoughlin/swift,shahmishal/swift,gribozavr/swift,hooman/swift,stephentyrone/swift,devincoughlin/swift,hooman/swift,ahoppen/swift,shajrawi/swift,xwu/swift,roambotics/swift,harlanhaskins/swift,tkremenek/swift,gribozavr/swift,devincoughlin/swift,stephentyrone/swift,shajrawi/swift,xwu/swift,benlangmuir/swift,rudkx/swift,tkremenek/swift,benlangmuir/swift,karwa/swift,nathawes/swift,devincoughlin/swift,gregomni/swift,CodaFi/swift,rudkx/swift,glessard/swift,hooman/swift,shajrawi/swift,benlangmuir/swift,gregomni/swift,lorentey/swift,atrick/swift,xwu/swift,apple/swift,jmgc/swift,apple/swift,aschwaighofer/swift,roambotics/swift,stephentyrone/swift,shahmishal/swift,xedin/swift,stephentyrone/swift,xedin/swift,JGiola/swift,rudkx/swift,karwa/swift,gribozavr/swift,jmgc/swift,sschiau/swift,shahmishal/swift,stephentyrone/swift,roambotics/swift,shajrawi/swift,shajrawi/swift,allevato/swift,jckarter/swift,parkera/swift,karwa/swift,glessard/swift,JGiola/swift,harlanhaskins/swift,atrick/swift,gregomni/swift,ahoppen/swift,shahmishal/swift,airspeedswift/swift,glessard/swift,CodaFi/swift,nathawes/swift,sschiau/swift,aschwaighofer/swift,parkera/swift,CodaFi/swift,xedin/swift,lorentey/swift,harlanhaskins/swift,gribozavr/swift,karwa/swift,lorentey/swift,benlangmuir/swift,tkremenek/swift,xedin/swift,CodaFi/swift,karwa/swift,shajrawi/swift,parkera/swift,karwa/swift,nathawes/swift,jmgc/swift,shahmishal/swift,JGiola/swift,lorentey/swift,airspeedswift/swift,airspeedswift/swift,xwu/swift,harlanhaskins/swift,gribozavr/swift,airspeedswift/swift,jckarter/swift,aschwaighofer/swift,roambotics/swift,devincoughlin/swift,lorentey/swift,rudkx/swift,devincoughlin/swift,glessard/swift,xedin/swift,gregomni/swift,lorentey/swift,jmgc/swift,ahoppen/swift,xedin/swift,glessard/swift,stephentyrone/swift,shahmishal/swift,nathawes/swift