Remove a long-standing __has_include hack.

This was put in to get libc++ building without libcxxabi. We now have
macros that show that we are building against libcxxabi so use that
instead. This guards against existing but broken cxxabi.h headers on the
system.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@250507 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/exception.cpp b/src/exception.cpp
index 2c16060..e172f64 100644
--- a/src/exception.cpp
+++ b/src/exception.cpp
@@ -12,10 +12,6 @@
 #include "exception"
 #include "new"
 
-#ifndef __has_include
-#define __has_include(inc) 0
-#endif
-
 #if defined(__APPLE__) && !defined(LIBCXXRT)
   #include <cxxabi.h>
 
@@ -29,16 +25,16 @@
     #define __terminate_handler  __cxxabiapple::__cxa_terminate_handler
     #define __unexpected_handler __cxxabiapple::__cxa_unexpected_handler
   #endif  // _LIBCPPABI_VERSION
-#elif defined(LIBCXXRT) || defined(LIBCXX_BUILDING_LIBCXXABI) || __has_include(<cxxabi.h>)
+#elif defined(LIBCXXRT) || defined(LIBCXX_BUILDING_LIBCXXABI)
   #include <cxxabi.h>
   using namespace __cxxabiv1;
   #if defined(LIBCXXRT) || defined(_LIBCPPABI_VERSION)
     #define HAVE_DEPENDENT_EH_ABI 1
   #endif
-#elif !defined(__GLIBCXX__) // __has_include(<cxxabi.h>)
+#elif !defined(__GLIBCXX__) // defined(LIBCXX_BUILDING_LIBCXXABI)
   static std::terminate_handler  __terminate_handler;
   static std::unexpected_handler __unexpected_handler;
-#endif // __has_include(<cxxabi.h>)
+#endif // defined(LIBCXX_BUILDING_LIBCXXABI)
 
 namespace std
 {
diff --git a/src/new.cpp b/src/new.cpp
index 1144651..f4f73d8 100644
--- a/src/new.cpp
+++ b/src/new.cpp
@@ -13,10 +13,6 @@
 
 #include "new"
 
-#ifndef __has_include
-#define __has_include(inc) 0
-#endif
-
 #if defined(__APPLE__) && !defined(LIBCXXRT)
     #include <cxxabi.h>
 
@@ -27,9 +23,9 @@
         #define __new_handler __cxxabiapple::__cxa_new_handler
     #endif
 #else  // __APPLE__
-    #if defined(LIBCXXRT) || __has_include(<cxxabi.h>)
+    #if defined(LIBCXXRT) || defined(LIBCXX_BUILDING_LIBCXXABI)
         #include <cxxabi.h>
-    #endif  // __has_include(<cxxabi.h>)
+    #endif  // defined(LIBCXX_BUILDING_LIBCXXABI)
     #if !defined(_LIBCPPABI_VERSION) && !defined(__GLIBCXX__)
         static std::new_handler __new_handler;
     #endif  // _LIBCPPABI_VERSION
diff --git a/src/stdexcept.cpp b/src/stdexcept.cpp
index aff4b18..577376e 100644
--- a/src/stdexcept.cpp
+++ b/src/stdexcept.cpp
@@ -13,12 +13,8 @@
 #include "string"
 #include "system_error"
 
-#ifndef __has_include
-#define __has_include(inc) 0
-#endif
-
 /* For _LIBCPPABI_VERSION */
-#if __has_include(<cxxabi.h>) || defined(__APPLE_) || defined(LIBCXXRT)
+#if defined(LIBCXX_BUILDING_LIBCXXABI) || defined(__APPLE_) || defined(LIBCXXRT)
 #include <cxxabi.h>
 #endif
 
diff --git a/src/typeinfo.cpp b/src/typeinfo.cpp
index b428120..5c0a609 100644
--- a/src/typeinfo.cpp
+++ b/src/typeinfo.cpp
@@ -8,13 +8,8 @@
 //===----------------------------------------------------------------------===//
 #include <stdlib.h>
 
-#ifndef __has_include
-#define __has_include(inc) 0
-#endif
-
-#ifdef __APPLE__
-#include <cxxabi.h>
-#elif defined(LIBCXXRT) || __has_include(<cxxabi.h>)
+#if defined(__APPLE__) || defined(LIBCXXRT) ||                                 \
+    defined(LIBCXX_BUILDING_LIBCXXABI)
 #include <cxxabi.h>
 #endif