SDL: testffmpeg: treat Khronos headers as system headers

From 911fc9b17e943d1668e0890ed4d7d46ce4f5a195 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Thu, 18 Apr 2024 17:03:34 +0200
Subject: [PATCH] testffmpeg: treat Khronos headers as system headers

---
 test/CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index cba5a5b9deae5..890b880bd411c 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -247,7 +247,7 @@ if(FFmpeg_FOUND AND LIBAVUTIL_AVFRAME_HAS_CH_LAYOUT)
         target_link_libraries(testffmpeg PRIVATE OpenGL::EGL)
         target_compile_definitions(testffmpeg PRIVATE HAVE_EGL)
     endif()
-    target_include_directories(testffmpeg BEFORE PRIVATE ${SDL3_SOURCE_DIR}/src/video/khronos)
+    target_include_directories(testffmpeg SYSTEM BEFORE PRIVATE ${SDL3_SOURCE_DIR}/src/video/khronos)
     target_link_libraries(testffmpeg PRIVATE ${FFMPEG_LIBRARIES})
 else()
     message(STATUS "Can't find ffmpeg 5.1.3 or newer, skipping testffmpeg")