tty-clock: pull pending upstream inclusion fix for ncurses-6.3

Without the fix build on ncurses-6.3 fails as:

    ttyclock.c:270:71: error: format not a string literal and no format arguments [-Werror=format-security]
      270 |           mvwprintw(ttyclock.datewin, (DATEWINH / 2), 1, ttyclock.date.datestr);
          |                                                          ~~~~~~~~~~~~~^~~~~~~~

pkgs/tools/misc/tty-clock/default.nix

@@ -1,16 +1,27 @@
-{ lib, stdenv, fetchFromGitHub, ncurses, pkg-config }:
+{ lib, stdenv, fetchFromGitHub, fetchpatch, ncurses, pkg-config }:
 
 stdenv.mkDerivation rec {
   pname = "tty-clock";
-  version = "2.3";
+  version = "2.3+unstable=2021-04-07";
 
   src = fetchFromGitHub {
     owner = "xorg62";
     repo = "tty-clock";
-    rev = "v${version}";
-    sha256 = "16v3pmva13skpfjja96zacjpxrwzs1nb1iqmrp2qzvdbcm9061pp";
+    # Use unreleased version to pull in fix for ncurses-6.3
+    rev = "9e00c32098524c30dac4dab701f7e33f8bc7c880";
+    sha256 = "14jrzz06jr29887bxgad1x6kd26c2fnqrc26864wqm3838fpcqw0";
   };
 
+  patches = [
+    # Pull upstream patch pending inclusion fir more ncurses-6.3 fixes:
+    #  https://github.com/xorg62/tty-clock/pull/100
+    (fetchpatch {
+      name = "ncurses-6.2.patch";
+      url = "https://github.com/xorg62/tty-clock/commit/4cfd73080da1964557484da620c401745d73881c.patch";
+      sha256 = "13pj1v6yrfc4vynsa746974kixfxxsy2jzzpl73c8bp7msr9d3md";
+    })
+  ];
+
   nativeBuildInputs = [ pkg-config ];
   buildInputs = [ ncurses ];