AArch64: add support for ARM64 iOS versions of compiler-rt.

Just a dummy directory and a few sane choices in the Darwin SDK.

rdar://problem/18575597

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@219323 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit c1bdff019f0b948d949e535ebd91586f95ef7c42)
diff --git a/SDKs/darwin/usr/include/stdio.h b/SDKs/darwin/usr/include/stdio.h
index 629b450..1a8781f 100644
--- a/SDKs/darwin/usr/include/stdio.h
+++ b/SDKs/darwin/usr/include/stdio.h
@@ -34,7 +34,7 @@
 #    define __FDOPEN_NAME  "_fdopen"
 #    define __FOPEN_NAME "_fopen"
 #    define __FWRITE_NAME "_fwrite"
-#  elif defined(__arm)
+#  elif defined(__arm) || defined(__arm64)
 #    define __FDOPEN_NAME  "_fdopen"
 #    define __FOPEN_NAME "_fopen"
 #    define __FWRITE_NAME "_fwrite"
@@ -46,7 +46,7 @@
 #    define __FDOPEN_NAME  "_fdopen"
 #    define __FOPEN_NAME "_fopen"
 #    define __FWRITE_NAME "_fwrite"
-#  elif defined(__arm)
+#  elif defined(__arm) || defined(__arm64)
 #    define __FDOPEN_NAME  "_fdopen"
 #    define __FOPEN_NAME "_fopen"
 #    define __FWRITE_NAME "_fwrite"