Fix conditionals on __Unwind_SjLj_* functions to only build for SJLJ based architectures

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@192241 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/Unwind/Unwind_AppleExtras.cpp b/src/Unwind/Unwind_AppleExtras.cpp
index ef09e4f..6d02a66 100644
--- a/src/Unwind/Unwind_AppleExtras.cpp
+++ b/src/Unwind/Unwind_AppleExtras.cpp
@@ -183,10 +183,11 @@
 }
 
 
-#if !FOR_DYLD
+#if !FOR_DYLD && _LIBUNWIND_BUILD_SJLJ_APIS
 
 #include <System/pthread_machdep.h>
 
+// Accessors to get get/set linked list of frames for sjlj based execeptions.
 _LIBUNWIND_HIDDEN
 struct _Unwind_FunctionContext *__Unwind_SjLj_GetTopOfFunctionStack() {
   return (struct _Unwind_FunctionContext *)