Replace fts-dev with musl-fts-dev under alpine

[sulisu]

Package name for fts-dev in alpine is "musl-fts-dev", and musl-fts for fts.

And util-linux-misc is available in 3.17. At least there is no util-linux-misc in 3.14 repo.

Install mount and umont from repo, busybox version doesn't work for this script.

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[tux-ware]

I hope that fixes proposed by sulisu will be included soon. This repo has one of the best and most recent zram-config solutions right now, despite not seeing any commits during the last year or so.

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[ecdye]

This seems like a great idea, I've been away for some time, and I also don't have a system to test these particular changes on. Would you be willing to open a pr for this @sulisu?