Revert "[libc++] Take 3: Do not cleverly link against libc++abi just because it happens to be there"

This also reverts "[libc++] Remove temporary hack for D63883".
Clearly, I don't understand how the Linux build bots are configured.

Differential Revision: https://reviews.llvm.org/D63883

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@368238 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -148,11 +148,34 @@ set(LIBCXX_CXX_ABI "default" CACHE STRING
 set(CXXABIS none default libcxxabi libcxxrt libstdc++ libsupc++ vcruntime)
 set_property(CACHE LIBCXX_CXX_ABI PROPERTY STRINGS ;${CXXABIS})
 
+# FIXME: This is a temporary hack to get the buildbots working while D63883 is in flight.
+# Without this all the bots fail while building libc++
+if (DEFINED ENV{USER})
+  if (("$ENV{USER}" STREQUAL "buildbot") OR (("$ENV{USER}" STREQUAL "llvmbb") OR ("$ENV{USER}" STREQUAL "buildslave")))
+    if (LIBCXX_CXX_ABI STREQUAL "libcxxabi" AND NOT DEFINED LIBCXX_CXX_ABI_INCLUDE_PATHS)
+      message(WARNING "OVERRIDING BUILDBOT CONFIG")
+      set(LIBCXX_CXX_ABI "default" CACHE STRING "FIXME" FORCE)
+    endif()
+  endif()
+endif()
 # Setup the default options if LIBCXX_CXX_ABI is not specified.
 if (LIBCXX_CXX_ABI STREQUAL "default")
+  find_path(
+    LIBCXX_LIBCXXABI_INCLUDES_INTERNAL cxxabi.h
+    PATHS ${LLVM_MAIN_SRC_DIR}/projects/libcxxabi/include
+          ${LLVM_MAIN_SRC_DIR}/runtimes/libcxxabi/include
+          ${LLVM_MAIN_SRC_DIR}/../libcxxabi/include
+    NO_DEFAULT_PATH
+    NO_CMAKE_FIND_ROOT_PATH
+  )
   if (LIBCXX_TARGETING_MSVC)
     # FIXME: Figure out how to configure the ABI library on Windows.
     set(LIBCXX_CXX_ABI_LIBNAME "vcruntime")
+  elseif ((NOT LIBCXX_STANDALONE_BUILD OR HAVE_LIBCXXABI) AND
+          IS_DIRECTORY "${LIBCXX_LIBCXXABI_INCLUDES_INTERNAL}")
+    set(LIBCXX_CXX_ABI_LIBNAME "libcxxabi")
+    set(LIBCXX_CXX_ABI_INCLUDE_PATHS "${LIBCXX_LIBCXXABI_INCLUDES_INTERNAL}")
+    set(LIBCXX_CXX_ABI_INTREE 1)
   elseif (APPLE)
     set(LIBCXX_CXX_ABI_LIBNAME "libcxxabi")
     set(LIBCXX_CXX_ABI_SYSTEM 1)

cmake/Modules/HandleLibCXXABI.cmake

@@ -98,7 +98,7 @@ if ("${LIBCXX_CXX_ABI_LIBNAME}" STREQUAL "libstdc++" OR
     "${_LIBSUPCXX_LIBNAME}" "${_LIBSUPCXX_LIBNAME}" "${_LIBSUPCXX_INCLUDE_FILES}" "bits"
     )
 elseif ("${LIBCXX_CXX_ABI_LIBNAME}" STREQUAL "libcxxabi")
-  if (TARGET cxxabi_shared AND TARGET cxxabi_static)
+  if (LIBCXX_CXX_ABI_INTREE)
     # Link against just-built "cxxabi" target.
     set(CXXABI_SHARED_LIBNAME cxxabi_shared)
     set(CXXABI_STATIC_LIBNAME cxxabi_static)