This fixes the Windows linker 4217 warning seen when building swift-corelibs-foundation for windows, when IRGen adds 'dllimport' to the _bridgeToObjectiveC IR reference within the same Swift module
The exact warning fixed: warning LNK4217: symbol 'sSS10FoundationE19_bridgeToObjectiveCAA8NSStringCyF' defined in 'Bridging.swift.obj' is imported by 'NSSet.swift.obj' in function 's10Foundation5NSSetC3set9copyItemsACShys11AnyHashableVG_SbtcfC'