check if a symbolic link already exists

[garasubo]

Fix #4

Add check before creating symbolic link to prevent ln command failure

[rui314]

I'm not a self hosted runner user so I don't know if it is reasonable to destructively overwrite a system command using a GitHub actions. It is ultimately a users responsibility to installing GitHub actions, but is it commonly expected?

[garasubo]

I think in most case, a self hosted runner is built on independent environment, like VM, AWS instances, and things like that. So, sometimes, it needs to overwrite a system command using a GitHub Action

[rui314]

OK, if a user want to use this Action, it's ultimately their responsibility to use it correctly.