glx: Fix up glXQueryGLXPbufferSGIX on macOS.

Fix this build error on macOS.

../src/glx/apple/glx_empty.c:158:4: error: void function 'glXQueryGLXPbufferSGIX' should not return a value [-Wreturn-type]
   return 0;
   ^      ~

Fixes: 3dd299c3d5b8 ("glx: Sync <GL/glxext.h> with Khronos")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Adam Jackson <ajax@redhat.com>
1 file changed