rubyPackages.ruby-terminfo: fix ruby 3 build

`rubyio.h` was a backwards compatibility hack, removed in recent versions.
Use `ruby/io.h` instead.
`rb_cData` was deprecated in https://bugs.ruby-lang.org/issues/18433 and
removed in Ruby 3.2.

pkgs/development/ruby-modules/gem-config/default.nix

@@ -649,6 +649,13 @@ in
       "--with-cflags=-I${ncurses.dev}/include"
       "--with-ldflags=-L${ncurses.out}/lib"
     ];
+    dontBuild = false;
+    postPatch = ''
+      substituteInPlace extconf.rb --replace 'rubyio.h' 'ruby/io.h'
+      substituteInPlace terminfo.c \
+        --replace 'rubyio.h' 'ruby/io.h' \
+        --replace 'rb_cData' 'rb_cObject'
+    '';
   };
 
   ruby-vips = attrs: {