CMake: Don't link directly to libGL on Unix. (we always dynamically load it at runtime when appropriate.)
diff --git a/cmake/sdlchecks.cmake b/cmake/sdlchecks.cmake
index 7ff0985..c4616cc 100644
--- a/cmake/sdlchecks.cmake
+++ b/cmake/sdlchecks.cmake
@@ -679,7 +679,6 @@ macro(CheckOpenGLX11)
set(SDL_VIDEO_OPENGL 1)
set(SDL_VIDEO_OPENGL_GLX 1)
set(SDL_VIDEO_RENDER_OGL 1)
- list(APPEND EXTRA_LIBS GL)
endif()
endif()
endmacro()