this patch to the grub2 sources is taken from:

git.savannah.gnu.org/gitweb/?p=gnulib.git;a=patch;h=25df6dc4
github.com/coreutils/gnulib/commit/25df6dc4

From 25df6dc4253480a343dde3376ce6fd99c316a532 Mon Sep 17 00:00:00 2001
From: Bruno Haible <bruno@clisp.org>
Date: Thu, 3 Apr 2025 00:45:30 +0200
Subject: [PATCH] Silence some -Wunterminated-string-initialization warnings.

* lib/base32.c (base32_encode): Mark b32str as not NUL-terminated.
* lib/base64.c (b64c): Mark as not NUL-terminated.
* lib/bcp47.c (struct script): Mark the 'code' field as not
NUL-terminated.
* lib/striconveh.c (mem_cd_iconveh_internal): Mark hex as not
NUL-terminated.
* lib/unicase/special-casing.in.h (struct special_casing_rule): Mark the
'code' field as not NUL-terminated.


--- a/grub-core/lib/gnulib/base64.c
+++ b/grub-core/lib/gnulib/base64.c
@@ -59,7 +59,7 @@ to_uchar (char ch)
   return ch;
 }
 
-static const char b64c[64] =
+static const char b64c[64] _GL_ATTRIBUTE_NONSTRING =
   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
 /* Base64 encode IN array of size INLEN into OUT array. OUT needs