Fix backwards test that I committed yesterday. Sigh

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@357540 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/thread b/include/thread
index 400459a..3d8d2ac 100644
--- a/include/thread
+++ b/include/thread
@@ -436,9 +436,9 @@
     {
 #if defined(_LIBCPP_COMPILER_GCC) && (__powerpc__ || __POWERPC__)
     //  GCC's long double const folding is incomplete for IBM128 long doubles.
-        _LIBCPP_CONSTEXPR duration<long double> _Max = duration<long double>(ULLONG_MAX/1000000000ULL) ;
-#else
         _LIBCPP_CONSTEXPR duration<long double> _Max = nanoseconds::max();
+#else
+        _LIBCPP_CONSTEXPR duration<long double> _Max = duration<long double>(ULLONG_MAX/1000000000ULL) ;
 #endif
         nanoseconds __ns;
         if (__d < _Max)