Fix T102306: buildtime shader compilation option fails under Wayland

libdecor (for window decorations) was crashing on exit with the shader
builder, avoid the crash by calling the "background" system creation
function which doesn't initialize window management under Wayland.

source/blender/gpu/intern/gpu_shader_builder.cc

@@ -59,7 +59,7 @@ void ShaderBuilder::init()
       break;
   }
 
-  ghost_system_ = GHOST_CreateSystem();
+  ghost_system_ = GHOST_CreateSystemBackground();
   ghost_context_ = GHOST_CreateOpenGLContext(ghost_system_, glSettings);
   GHOST_ActivateOpenGLContext(ghost_context_);