Permissions trouble in compiling with stack

### General summary/comments (optional)
In attempting to build Eta (as covered here http://eta-lang.org/docs/html/getting-started.html), I ran into a number of errors with permissions, and was advised by the great guys over at their github to open an issue here. That thread can be found here: https://github.com/typelead/eta/issues/238

### Steps to reproduce
cd into the directory Eta was cloned into and run ./install.sh.

### Expected
Expected to run it, get it compiled, and get going.

### Actual
Instead, I got a large number of errors relating to permissions, so I started doing --allow-different-user and running cleaninstall.sh as root. This resulted in what's seen in this gist: https://gist.github.com/ogkloo/66784cdfa2f8181195e7010b6dfd02ff

### Stack version
```
Version 1.4.0, Git revision e714f1dd3fade19496d91bd6a017e435a96a6bcd (4640 commits) x86_64 hpack-0.17.0
```

### Method of installation
Installed stack using:
`curl -sSL https://get.haskellstack.org/ | sh`
Then did stack update and upgrade. Interestingly, this also throws bugs for me if I don't run it with sudo, which requires the --allow-different-user flag, so I run:
```
$ sudo stack update --allow-different-user
$ sudo stack upgrade --allow-different-user
```
But I assume that's intentional since it modifies system files.