Revert "Revert "Update aosp/master libcxx rebase to r263688""

This reverts commit 1d4a1edbc7.

Change-Id: I2909937fe582f2c5552bc86e7f4d2d5cff0de0aa

test/std/containers/sequences/array/at.pass.cpp

@@ -7,6 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: libcpp-no-exceptions
 // <array>
 
 // reference operator[] (size_type)
@@ -19,7 +20,9 @@
 
 #include "test_macros.h"
 
-#include "suppress_array_warnings.h"
+// std::array is explicitly allowed to be initialized with A a = { init-list };.
+// Disable the missing braces warning for this reason.
+#include "disable_missing_braces_warning.h"
 
 int main()
 {