mecab: fix build with clang 16

Force the language mode to C++14. mecab-nodic uses several features that
have been removed from C++17.

pkgs/tools/text/mecab/base.nix

···
     "--with-charset=utf8"
   ];
 
+  # mecab uses several features that have been removed in C++17.
+  # Force the language mode to C++14, so that it can compile with clang 16.
+  makeFlags = [ "CXXFLAGS=-std=c++14" ];
+
   doCheck = true;
 }