build: silence linker warning (SR-9138)
build: silence linker warning (SR-9138)

We currently emit a symbol multiply when building a single module.
Ideally, we would ensure that they are marked for COMDAT and given
LinkOnceODR linkage to ensure that they are preserved.  This makes
errors in the link step more visible.

parkera/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation,parkera/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation