Piping to wl-copy causes Xwayland to launch

[Kacper-Kondracki]

When invoking echo "hello" | wl-copy Xwayland instance is launched.
But when invoking wl-copy hello it doesn't launch Xwayland.

So programs that use wl-clipboard and communicate with wl-copy via stdin, will spawn xwayland because of this, which is not desirable.
zyedidia/micro#3017

[bugaevc]

Hi, this is most likely caused by us invoking xdg-mime, and that in turn invoking something that references X11. This should go away one we switch away from using xdg-mime.