guile: Silence GC warnings on the Hurd.

This should work around <https://issues.guix.gnu.org/73181>, resurrecting
offloading to the Hurd.

* gnu/packages/aux-files/guile-launcher.c (no_warnings)[__GNU__]: New
function.
(main)[__GNU__]: Use it to silence libgc warnings.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>.
Change-Id: I8f30732d192ce46144da4a1a081813a104a5f376

gnu/packages/aux-files/guile-launcher.c

@@ -1,7 +1,8 @@
 /* GNU Guix --- Functional package management for GNU
    Copyright 1996-1997,2000-2001,2006,2008,2011,2013,2018,2020,2021
       Free Software Foundation, Inc.
-   Copyright (C) 2020 Ludovic Courtès <ludo@gnu.org>
+   Copyright (C) 2020, 2024 Ludovic Courtès <ludo@gnu.org>
+   Copyright (C) 2024 Janneke Nieuwenhuizen <janneke@gnu.org>
 
    This file is part of GNU Guix.
 
@@ -28,6 +29,14 @@
 #include <locale.h>
 #include <libguile.h>
 
+#if defined __GNU__
+#include <gc.h>
+static void
+no_warnings (char *message, GC_word arg)
+{
+}
+#endif
+
 /* Saved values of GUILE_LOAD_PATH and GUILE_LOAD_COMPILED_PATH.  */
 static const char *load_path, *load_compiled_path;
 
@@ -73,6 +82,14 @@ main (int argc, char **argv)
        which is always preferable over the C locale.  */
     setlocale (LC_ALL, "en_US.utf8");
 
+#if defined __GNU__
+  /* XXX: On 32-bit GNU/Hurd (i586-gnu), libgc emits "Repeated allocation"
+     warnings that are annoying and interfere with communications between
+     'guix-daemon' and 'guix authenticate':
+     <https://issues.guix.gnu.org/73181>.  Silence them.  */
+  GC_set_warn_proc (no_warnings);
+#endif
+
   const char *str;
   str = getenv ("GUILE_LOAD_PATH");
   load_path = str != NULL ? strdup (str) : NULL;