Disable -Wsuggest-override for all remaining unittests/ directories

GitOrigin-RevId: 21c0b4c1e8d6a171899b31d072a47dac27258fc5
diff --git a/unittests/CMakeLists.txt b/unittests/CMakeLists.txt
index fac7038..1a05849 100644
--- a/unittests/CMakeLists.txt
+++ b/unittests/CMakeLists.txt
@@ -19,6 +19,10 @@
   target_link_libraries(${test_name} PRIVATE Polly)
 endfunction()
 
+if (CXX_SUPPORTS_SUGGEST_OVERRIDE_FLAG)
+  add_definitions("-Wno-suggest-override")
+endif()
+
 add_subdirectory(Isl)
 add_subdirectory(Flatten)
 add_subdirectory(DeLICM)