SDL_mixer: Fixed a -Wstrict-aliasing warning from old gcc:

SDL Commits
1 
From 21f9e67061be0937a036af468b4543cb2a54bd35 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Mon, 28 Jul 2025 17:00:50 +0300
Subject: [PATCH] Fixed a -Wstrict-aliasing warning from old gcc:

src/SDL_mixer_metadata_tags.c: In function 'get_musicmatch_len':
src/SDL_mixer_metadata_tags.c:873: warning: dereferencing type-punned pointer will break strict-aliasing rules
---
 src/SDL_mixer_metadata_tags.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/SDL_mixer_metadata_tags.c b/src/SDL_mixer_metadata_tags.c
index 6fe00a77..651615ec 100644
--- a/src/SDL_mixer_metadata_tags.c
+++ b/src/SDL_mixer_metadata_tags.c
@@ -868,9 +868,9 @@ static Sint64 get_musicmatch_len(SDL_IOStream *io)
     // unused section: (4 bytes of 0x00)
     if (SDL_SeekIO(io, -(len + 4), SDL_IO_SEEK_END) == -1) {
         return -1;
-    } else if (SDL_ReadIO(io, buf, 4) != 4) {
+    } else if (SDL_ReadIO(io, &j, 4) != 4) {
         return -1;
-    } else if (*((Uint32 *) buf) != 0) {
+    } else if (j != 0) {
         return -1;
     }
     #endif