cre2: fix build

failed because of a single missing include; patch sent upstream

pkgs/by-name/cr/cre2/missing-header-include-pr-34.patch

@@ -0,0 +1,20 @@
+From 7c83c012b33a16b11e3547894118fc013ec23ca0 Mon Sep 17 00:00:00 2001
+From: Willy <jemand771@gmx.net>
+Date: Tue, 5 May 2026 13:50:44 +0200
+Subject: [PATCH] add missing cstring include
+
+fails on newer compilers/toolchains without
+---
+ src/cre2.cpp | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/src/cre2.cpp b/src/cre2.cpp
+index 5a63b93..3b1ec21 100644
+--- a/src/cre2.cpp
++++ b/src/cre2.cpp
+@@ -18,6 +18,7 @@
+ 
+ #include <cstdlib>
+ #include <cstdio>
++#include <cstring>
+ #include <vector>

pkgs/by-name/cr/cre2/package.nix

@@ -20,6 +20,10 @@ stdenv.mkDerivation (finalAttrs: {
     sha256 = "1h9jwn6z8kjf4agla85b5xf7gfkdwncp0mfd8zwk98jkm8y2qx9q";
   };
 
+  patches = [
+    ./missing-header-include-pr-34.patch
+  ];
+
   nativeBuildInputs = [
     autoreconfHook
     libtool