don't mount to /mnt or anywhere that is common

[Kyuunex]

I was using this script today to install arch on an external drive while being booted on my main arch system. this caused some problems because I already had stuff mounted /mnt because this is the most common place to mount external drives, in my case, i had other external drives mounted. So I had to edit the archfi script and change all references to /mnt to something else.

It would be nice if this was changed in the script so a user does not have to do it every time they wanna install arch while being booted to their existing arch install.

change it to /archfi-tmp or something that is just not commonly used.

[MatMoul]

PR #164 seem linked to your request...