SDL_image: cmake: disable shared PNG target when it is not needed

SDL Commits
1 
From c349aad209f843fad98b2f9da51e2a519d551d81 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Tue, 6 Jan 2026 16:03:58 +0100
Subject: [PATCH] cmake: disable shared PNG target when it is not needed

---
 CMakeLists.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1e47e0c8..5a85211e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -825,6 +825,7 @@ list(APPEND SDLIMAGE_BACKENDS PNG)
 set(SDLIMAGE_PNG_ENABLED FALSE)
 if(SDLIMAGE_PNG_LIBPNG)
     if(SDLIMAGE_PNG_VENDORED)
+        set(PNG_SHARED "${SDLIMAGE_PNG_SHARED}")
         set(SDLIMAGE_PNG_ENABLED TRUE)
         message(STATUS "${PROJECT_NAME}: Using vendored libpng")
         set(PNG_TESTS OFF CACHE BOOL "Build PNG Tests" FORCE)