[libcxx] Fixed build break on buildbots with -Werror

libcxx/utils/libcxx/test/params.py

@@ -13,6 +13,7 @@ _warningFlags = [
   '-Werror',
   '-Wall',
   '-Wextra',
+  '-Wno-deprecated-copy',
   '-Wshadow',
   '-Wundef',
   '-Wno-unused-command-line-argument',