LowerBitSets: Do not export symbols for bit set referenced globals on Darwin.

The linker on that platform may re-order symbols or strip dead symbols, which
will break bit set checks. Avoid this by hiding the symbols from the linker.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232235 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed