[libc++] Remove old workaround for buildit

Summary:
I'm not sure what the problem was at the time, however I don't think
this is necessary since buildit doesn't exist anymore.

Instead of the workaround, the correct thing to do is to leave out
the get_new_handler/set_new_handler definitions from libc++ when
we're getting them from libc++abi.

Reviewers: EricWF

Subscribers: christof, jkorous, dexonsmith, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D60717

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@358518 91177308-0d34-0410-b5e6-96231b3b80d8

src/new.cpp

@@ -22,12 +22,8 @@
 #   include "support/runtime/new_handler_fallback.ipp"
 #elif defined(__GLIBCXX__)
     // nothing to do
-#else
-#   if defined(__APPLE__) && !defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY)
-#       include <cxxabi.h> // FIXME: remove this once buildit is gone.
-#   else
-#       include "support/runtime/new_handler_fallback.ipp"
-#   endif
+#elif !defined(_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS)
+#   include "support/runtime/new_handler_fallback.ipp"
 #endif
 
 namespace std