[MIPS] Fix atomic_is_lock_free test for mips32.
On 32-bit MIPS, 64-bit atomic ops are achieved through locks.
So allow the test to fail for atomic_intmax_t on 32-bit MIPS.

(cherry picked from commit f1837377d215a6eda294b6ac7552b226deee91ce)

Change-Id: I973d999c31c9ab89b5a7b709beff6486b93408f2
diff --git a/tests/stdatomic_test.cpp b/tests/stdatomic_test.cpp
index d41bfa9..5e88c88 100644
--- a/tests/stdatomic_test.cpp
+++ b/tests/stdatomic_test.cpp
@@ -66,7 +66,12 @@
   atomic_char small;
   atomic_intmax_t big;
   ASSERT_TRUE(atomic_is_lock_free(&small));
+  // atomic_intmax_t(size = 64) is not lock free on mips32.
+#if defined(__mips__) && !defined(__LP64__)
+  ASSERT_FALSE(atomic_is_lock_free(&big));
+#else
   ASSERT_TRUE(atomic_is_lock_free(&big));
+#endif
 }
 
 TEST(stdatomic, atomic_flag) {