Fixes LTO build
https://github.com/eggheads/eggdrop/commit/e826fffc93e1dcfaa0e7d23c2a6c8e8c036f0f4b

From e826fffc93e1dcfaa0e7d23c2a6c8e8c036f0f4b Mon Sep 17 00:00:00 2001
From: Michael Ortmann <41313082+michaelortmann@users.noreply.github.com>
Date: Thu, 27 Nov 2025 18:56:55 +0100
Subject: [PATCH] Fix type mismatch

--- a/src/main.c
+++ b/src/main.c
@@ -83,7 +83,7 @@ extern sigjmp_buf alarmret;
 time_t now;
 static int argc;
 static char **argv;
-char *argv0;
+const char *argv0;
 
 /*
  * Please use the PATCH macro instead of directly altering the version
@@ -471,7 +471,7 @@ static void show_help() {
          "-t  Don't background; use terminal to simulate DCC chat.\n"
          "-m  Create userfile.\n"
          "-h  Show this help and exit.\n"
-         "-v  Show version info and exit.\n\n", argv[0]);
+         "-v  Show version info and exit.\n\n", argv0);
   bg_send_quit(BG_ABORT);
 }
 
--- a/src/modules.c
+++ b/src/modules.c
@@ -95,7 +95,7 @@ extern time_t now, online_since;
 extern tand_t *tandbot;
 extern Tcl_Interp *interp;
 extern sock_list *socklist;
-extern char argv0;
+extern const char *argv0;
 
 
 int xtra_kill();