[libcxx] Add support for linking libc++ against a static ABI library.

Summary:
This patch add the CMake option `LIBCXX_ENABLE_STATIC_ABI_LIBRARY` which, when enabled, will link libc++ against the static version of the ABI library.


Reviewers: mclow.lists, jroelofs, danalbert

Reviewed By: danalbert

Subscribers: compnerd, cfe-commits

Differential Revision: http://reviews.llvm.org/D8017

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@231076 91177308-0d34-0410-b5e6-96231b3b80d8

test/CMakeLists.txt

@@ -44,6 +44,11 @@ if (LIT_EXECUTABLE)
   pythonize_bool(LIBCXX_BUILD_32_BITS)
   pythonize_bool(LIBCXX_ENABLE_THREADS)
   pythonize_bool(LIBCXX_ENABLE_MONOTONIC_CLOCK)
+  # The tests shouldn't link to any ABI library when it has been linked into
+  # libc++ statically.
+  if (LIBCXX_ENABLE_STATIC_ABI_LIBRARY)
+    set(LIBCXX_CXX_ABI_LIBNAME "none")
+  endif()
   set(LIBCXX_TARGET_INFO "libcxx.test.target_info.LocalTI" CACHE STRING
       "TargetInfo to use when setting up test environment.")
   set(LIBCXX_EXECUTOR "None" CACHE STRING