SDL_image: cmake: use SDLIMAGE_ROOTPROJECT'

SDL Commits
1 
From 189306abb842853b90a1263654894223689372af Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Sat, 28 Dec 2024 01:24:31 +0100
Subject: [PATCH] cmake: use SDLIMAGE_ROOTPROJECT'

---
 CMakeLists.txt | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 731d1f96..aab1a542 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -32,9 +32,8 @@ else()
     set(SDLIMAGE_ROOTPROJECT OFF)
 endif()
 
-
 # By default, configure in RelWithDebInfo configuration
-if(NOT SDL3_SUBPROJECT)
+if(NOT SDLIMAGE_ROOTPROJECT)
     get_property(is_multi_config GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
     if(is_multi_config)
         # The first item in CMAKE_CONFIGURATION_TYPES is the default configuration