SDL_image: stb_image.h: silence set-but-unused warning.

SDL Commits
1 
From 6e636c28f1420201791ddda53061546ca9a1b170 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Thu, 9 Mar 2023 11:03:28 +0300
Subject: [PATCH] stb_image.h: silence set-but-unused warning.

---
 stb_image.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/stb_image.h b/stb_image.h
index 3a074858..6c559fb7 100644
--- a/stb_image.h
+++ b/stb_image.h
@@ -5352,6 +5352,7 @@ static int stbi__parse_png_file(stbi__png *z, int scan, int req_comp)
                invalid_chunk[1] = STBI__BYTECAST(c.type >> 16);
                invalid_chunk[2] = STBI__BYTECAST(c.type >>  8);
                invalid_chunk[3] = STBI__BYTECAST(c.type >>  0);
+               (void)invalid_chunk;
                #endif
                return stbi__err(invalid_chunk, "PNG not supported: unknown PNG chunk type");
             }