Move ARM failure from FIXME to XFAIL

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@221515 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/backtrace_test.cpp b/test/backtrace_test.cpp
index b41fdce..f54a478 100644
--- a/test/backtrace_test.cpp
+++ b/test/backtrace_test.cpp
@@ -6,6 +6,7 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+// XFAIL: arm
 #include <assert.h>
 #include <stddef.h>
 #include <unwind.h>
@@ -43,10 +44,6 @@
 }
 
 int main() {
-// FIXME: _Unwind_Backtrace is not clearly defined in EHABI and needs more
-// testing. A bug was created with some initial investigation done
-// http://llvm.org/PR21444. This test fails with both libunwind and libgcc_s.
-#ifndef __arm__
   size_t throw_ntraced = 0;
   size_t nothrow_ntraced = 0;
 
@@ -62,6 +59,5 @@
   // of times, so we can't make any better assumptions than this.
   assert(nothrow_ntraced > 1);
   assert(throw_ntraced == nothrow_ntraced); // Make sure we unwind through catch
-#endif
   return 0;
 }