SDL_image: cmake: don't add private PNG include properties to SDL3_image

SDL Commits
1 
From 8bab27f84fae438da13e4c2d861a943743b751f4 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Sun, 1 Feb 2026 20:49:56 +0100
Subject: [PATCH] cmake: don't add private PNG include properties to SDL3_image

The INTERFACE_SYSTEM_INCLUDE_DIRECTORIES property of PNG::PNG_shared might contain relative paths,
causing a CMake configure failure.

This is a bug in the PNG CMake scripts.
---
 CMakeLists.txt | 2 --
 1 file changed, 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 232892f7..e59a1de7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -900,9 +900,7 @@ if(SDLIMAGE_PNG)
                     set(png_target PNG::PNG)
                 endif()
                 target_include_directories(${sdl3_image_target_name} PRIVATE
-                    $<TARGET_PROPERTY:${png_target},INCLUDE_DIRECTORIES>
                     $<TARGET_PROPERTY:${png_target},INTERFACE_INCLUDE_DIRECTORIES>
-                    $<TARGET_PROPERTY:${png_target},INTERFACE_SYSTEM_INCLUDE_DIRECTORIES>
                 )
                 if(SDLIMAGE_PNG_VENDORED)
                     add_dependencies(${sdl3_image_target_name} ${png_target})