[Package] Fix passing -gline-tables-only when building.
[Package] Fix passing -gline-tables-only when building.

We should do regardless of whether we run the tests or not.
Also, clarify a comment while I'm here.

parkera/swift,xwu/swift,CodaFi/swift,nathawes/swift,roambotics/swift,hooman/swift,JGiola/swift,jmgc/swift,glessard/swift,hooman/swift,jmgc/swift,gregomni/swift,nathawes/swift,JGiola/swift,roambotics/swift,rudkx/swift,nathawes/swift,CodaFi/swift,CodaFi/swift,glessard/swift,hooman/swift,roambotics/swift,glessard/swift,nathawes/swift,tkremenek/swift,xwu/swift,apple/swift,benlangmuir/swift,jmgc/swift,tkremenek/swift,ahoppen/swift,jmgc/swift,xwu/swift,JGiola/swift,tkremenek/swift,rudkx/swift,tkremenek/swift,apple/swift,atrick/swift,atrick/swift,ahoppen/swift,tkremenek/swift,xwu/swift,ahoppen/swift,hooman/swift,tkremenek/swift,atrick/swift,glessard/swift,benlangmuir/swift,benlangmuir/swift,CodaFi/swift,parkera/swift,hooman/swift,parkera/swift,parkera/swift,apple/swift,JGiola/swift,benlangmuir/swift,atrick/swift,gregomni/swift,hooman/swift,benlangmuir/swift,jmgc/swift,roambotics/swift,ahoppen/swift,gregomni/swift,parkera/swift,rudkx/swift,xwu/swift,CodaFi/swift,jmgc/swift,glessard/swift,rudkx/swift,JGiola/swift,xwu/swift,CodaFi/swift,jmgc/swift,roambotics/swift,gregomni/swift,roambotics/swift,benlangmuir/swift,rudkx/swift,nathawes/swift,hooman/swift,JGiola/swift,ahoppen/swift,apple/swift,tkremenek/swift,atrick/swift,CodaFi/swift,ahoppen/swift,parkera/swift,gregomni/swift,apple/swift,nathawes/swift,apple/swift,nathawes/swift,parkera/swift,rudkx/swift,gregomni/swift,glessard/swift,xwu/swift,parkera/swift,atrick/swift