[Runtime] Weakly import dyld protocol conformance functions.
[Runtime] Weakly import dyld protocol conformance functions.

This allows us to build against a macOS 12 SDK and test on macOS 11.

rdar://81133606

JGiola/swift,glessard/swift,atrick/swift,JGiola/swift,ahoppen/swift,glessard/swift,benlangmuir/swift,xwu/swift,ahoppen/swift,roambotics/swift,hooman/swift,glessard/swift,JGiola/swift,glessard/swift,apple/swift,atrick/swift,roambotics/swift,roambotics/swift,ahoppen/swift,rudkx/swift,hooman/swift,atrick/swift,gregomni/swift,benlangmuir/swift,rudkx/swift,hooman/swift,apple/swift,rudkx/swift,JGiola/swift,gregomni/swift,hooman/swift,benlangmuir/swift,gregomni/swift,xwu/swift,benlangmuir/swift,roambotics/swift,xwu/swift,apple/swift,ahoppen/swift,atrick/swift,glessard/swift,roambotics/swift,gregomni/swift,ahoppen/swift,apple/swift,apple/swift,xwu/swift,xwu/swift,benlangmuir/swift,atrick/swift,benlangmuir/swift,hooman/swift,glessard/swift,rudkx/swift,roambotics/swift,gregomni/swift,xwu/swift,gregomni/swift,apple/swift,JGiola/swift,ahoppen/swift,rudkx/swift,atrick/swift,rudkx/swift,JGiola/swift,xwu/swift,hooman/swift,hooman/swift