sdl2-compat: Build testnative on UNIX with X11 support

SDL Commits
1 
From 208cea955f571e0ff967f04f6bb04f7e5018070c Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Sun, 19 Jan 2025 08:18:03 -0800
Subject: [PATCH] Build testnative on UNIX with X11 support

---
 test/CMakeLists.txt | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 38a93bc..03f86f5 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -119,6 +119,9 @@ elseif(UNIX AND NOT ANDROID)
   set(TESTNATIVE_EXTRA "testnativex11.c")
 endif()
 test_program(testnative SRC "testnative.c" "testutils.c" "${TESTNATIVE_EXTRA}")
+if(UNIX AND NOT ANDROID AND NOT APPLE)
+  target_link_libraries(testnative PRIVATE X11)
+endif()
 test_program(testoverlay2 SRC "testoverlay2.c" "testutils.c" "testyuv_cvt.c")
 test_program(testplatform NONINTERACTIVE SRC "testplatform.c")
 test_program(testpower NONINTERACTIVE SRC "testpower.c")