[staging-next] csdr: fix build with GCC 14 for ARM (#366762)

Author: fpletz

pkgs/by-name/cs/csdr/package.nix

@@ -19,6 +19,11 @@ stdenv.mkDerivation rec {
     sha256 = "sha256-LdVzeTTIvDQIXRdcz/vpQu/fUgtE8nx1kIEfoiwxrUg=";
   };
 
+  postPatch = ''
+    # function is not defined in any headers but used in libcsdr.c
+    echo "int errhead();" >> src/predefined.h
+  '';
+
   nativeBuildInputs = [
     cmake
     pkg-config