[libc++] Remove redundant conditionals for Apple platforms

Summary:
In a bunch of places, we used to check whether LIBCXX_BUILDING_LIBCXXABI
is defined OR we're building for an Apple platform. This used to
be necessary in a time when Apple's build script did NOT define
LIBCXX_BUILDING_LIBCXXABI. However this is not relevant anymore
since Apple's build does define LIBCXX_BUILDING_LIBCXXABI.

Reviewers: EricWF

Subscribers: christof, jkorous, dexonsmith, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D60842

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@358988 91177308-0d34-0410-b5e6-96231b3b80d8

src/exception.cpp

@@ -10,8 +10,7 @@
 #include "new"
 #include "typeinfo"
 
-#if defined(LIBCXXRT) || defined(LIBCXX_BUILDING_LIBCXXABI) || \
-  (defined(__APPLE__) && !defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY))
+#if defined(LIBCXXRT) || defined(LIBCXX_BUILDING_LIBCXXABI)
   #include <cxxabi.h>
   using namespace __cxxabiv1;
   #define HAVE_DEPENDENT_EH_ABI 1

src/support/runtime/stdexcept_default.ipp

@@ -10,8 +10,7 @@
 
 /* For _LIBCPPABI_VERSION */
 #if !defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY) &&                           \
-    (defined(LIBCXX_BUILDING_LIBCXXABI) || defined(__APPLE__) ||               \
-     defined(LIBCXXRT))
+    (defined(LIBCXX_BUILDING_LIBCXXABI) || defined(LIBCXXRT))
 #include <cxxabi.h>
 #endif
 

src/typeinfo.cpp

@@ -45,11 +45,11 @@ size_t std::type_info::hash_code() const _NOEXCEPT {
 }
 #endif // _LIBCPP_ABI_MICROSOFT
 
-// FIXME: Remove __APPLE__ default here once buildit is gone.
 // FIXME: Remove the _LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY configuration.
-#if (!defined(LIBCXX_BUILDING_LIBCXXABI) && !defined(LIBCXXRT) &&              \
-     !defined(__GLIBCXX__) && !defined(__APPLE__) &&                           \
-     !defined(_LIBCPP_ABI_VCRUNTIME)) ||   \
+#if (!defined(LIBCXX_BUILDING_LIBCXXABI) &&               \
+     !defined(LIBCXXRT) &&                                \
+     !defined(__GLIBCXX__) &&                             \
+     !defined(_LIBCPP_ABI_VCRUNTIME)) ||                  \
     defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY)
 std::type_info::~type_info()
 {