[libunwind] Add support for a single-threaded libunwind build

The EHABI unwinder is thread-agnostic, SJLJ unwinder and the DWARF unwinder have
a couple of pthread dependencies.

This patch makes it possible to build the whole of libunwind for a
single-threaded environment.

Reviewers: compnerd

Differential revision: https://reviews.llvm.org/D24984

git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@282575 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed
tree: 939e15e22c7536993825d33ca8af1a914b26b8a6
  1. .arcconfig
  2. .clang-format
  3. CMakeLists.txt
  4. cmake/
  5. include/
  6. src/
  7. test/