SDL_mixer: music_wavpack.c: Fixed warning

SDL Commits
1 
From d242875514a4765b2514b5143e212b9182aa741c Mon Sep 17 00:00:00 2001
From: Wohlstand <[EMAIL REDACTED]>
Date: Fri, 23 Dec 2022 17:10:27 +0300
Subject: [PATCH] music_wavpack.c: Fixed warning

---
 src/codecs/music_wavpack.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/codecs/music_wavpack.c b/src/codecs/music_wavpack.c
index 4e318a96..d1ead3db 100644
--- a/src/codecs/music_wavpack.c
+++ b/src/codecs/music_wavpack.c
@@ -243,6 +243,7 @@ static int sdl_setpos_abs32(void *id, uint32_t pos)
 
 static int sdl_pushback_byte(void *id, int c)
 {
+    (void)c;
     /* libwavpack calls ungetc(), but doesn't really modify buffer. */
     return (SDL_RWseek((SDL_RWops*)id, -1, RW_SEEK_CUR) < 0)? -1 : 0;
 }