string-concatenation build warning as error with clang 13 on macOS aarch64

We run into this error when compiling with clang version 13.0.0 (clang-1300.0.29.3) :

/test/hotspot/gtest/logging/logTestUtils.inline.hpp:35:70: error: suspicious concatenation of string literals in an array initialization; did you mean to separate the elements with a comma? [-Werror,-Wstring-concatenation]
  "=", "+", " ", "+=", "+=*", "*+", " +", "**", "++", ".", ",", ",," ",+",

Looks like the is a "," missing ?