sdl2-compat: Fix building tests without X11.

SDL Commits
1 
From 0d1ebe082a9c5d688d504fe8a9e6a07096855d15 Mon Sep 17 00:00:00 2001
From: vanfanel <[EMAIL REDACTED]>
Date: Mon, 3 Nov 2025 21:02:13 +0100
Subject: [PATCH] Fix building tests without X11.

---
 test/CMakeLists.txt | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 5c831ba..d86e81e 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -115,14 +115,14 @@ if(APPLE)
 elseif(WIN32)
   set(TESTNATIVE_EXTRA "testnativew32.c")
 elseif(UNIX AND NOT ANDROID)
-  if(NOT SDL2COMPAT_DISABLE_X11)
+  if(SDL2COMPAT_X11)
     find_package(X11 REQUIRED)
     set(TESTNATIVE_EXTRA "testnativex11.c")
   endif()
 endif()
 test_program(testnative SRC "testnative.c" "testutils.c" "${TESTNATIVE_EXTRA}")
 if(UNIX AND NOT ANDROID AND NOT APPLE)
-  if(NOT SDL2COMPAT_DISABLE_X11)
+  if(SDL2COMPAT_X11)
     target_link_libraries(testnative PRIVATE X11)
   endif()
 endif()