Support: Support LLVM_ENABLE_THREADS=0 in llvm/Support/thread.h.

Specifically, the header now provides llvm::thread, which is either a
typedef of std::thread or a replacement that calls the function synchronously
depending on the value of LLVM_ENABLE_THREADS.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246402 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed