[ORC] Remove a workaround for systems lacking 8-byte atomics.

SymbolStringPool ref counts are now size_t, rather than uint64_t, so I do not
think this is necessary any more.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@340704 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed