[PATCH] Support building libc++ using an in-tree libc++abi

[eatnumber1 at google.com]

From: Russell Harmon <eatnumber1 at google.com>

This will detect if you are building libcxx in-tree and libcxxabi is available.
If so, it will default to using the in-tree libcxxabi by setting LIBCXX_CXX_ABI
to "libcxxabi", LIBCXX_LIBCXXABI_INCLUDE_PATHS to
"${CMAKE_SOURCE_DIR}/projects/libcxxabi/include" and will add "cxxabi" as a
proper dependency.
---
 CMakeLists.txt | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c20e5d1..1345eef 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -46,7 +46,13 @@ option(LIBCXX_INSTALL_SUPPORT_HEADERS "Install libc++ support headers." ON)
 
 set(CXXABIS none libcxxabi libcxxrt libstdc++ libsupc++)
 if (NOT DEFINED LIBCXX_CXX_ABI)
-  set(LIBCXX_CXX_ABI "none")
+  if (NOT DEFINED LIBCXX_BUILT_STANDALONE AND IS_DIRECTORY "${CMAKE_SOURCE_DIR}/projects/libcxxabi")
+    set(LIBCXX_CXX_ABI "libcxxabi")
+    set(LIBCXX_LIBCXXABI_INCLUDE_PATHS "${CMAKE_SOURCE_DIR}/projects/libcxxabi/include")
+    set(LIBCXX_CXX_ABI_INTREE 1)
+  else ()
+    set(LIBCXX_CXX_ABI "none")
+  endif ()
 endif()
 set(LIBCXX_CXX_ABI "${LIBCXX_CXX_ABI}" CACHE STRING
     "Specify C++ ABI library to use." FORCE)
@@ -149,6 +155,10 @@ elseif ("${LIBCXX_CXX_ABI}" STREQUAL "libcxxabi")
   setup_abi_lib("LIBCXX_LIBCXXABI_INCLUDE_PATHS" ""
     "c++abi" "cxxabi.h" ""
     )
+
+  if (LIBCXX_CXX_ABI_INTREE)
+    add_dependencies(LIBCXX_CXX_ABI_DEPS cxxabi)
+  endif ()
 elseif ("${LIBCXX_CXX_ABI}" STREQUAL "libcxxrt")
   setup_abi_lib("LIBCXX_LIBCXXRT_INCLUDE_PATHS" "-DLIBCXXRT"
     "cxxrt" "cxxabi.h;unwind.h;unwind-arm.h;unwind-itanium.h" ""
-- 
2.0.0.526.g5318336