Correct nullability of free() redeclaration
Correct nullability of free() redeclaration

In the new clang, this declaration ends up influencing the redeclaration chain, altering the nullability of the `free(_:)` function imported into Swift.

Fixes rdar://71269128. Note that tests may fail unless a clean build is performed.

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