Git dependencies fail when they contain symlinks to outside the repository, or broken symlinks

### General summary/comments (optional)

We have https://github.com/shmish111/servant-purescript as a git dependency. New versions of Stack fail with a tarball error.

It seems there have been some issues in this vein already, e.g. https://github.com/commercialhaskell/stack/issues/4580.

### Steps to reproduce
Add
```
extra-deps:
- git: https://github.com/shmish111/servant-purescript.git
commit: ab14502279c92084f06aa6222a17873275279e63
```
to your `stack.yaml` and `stack build`.

### Expected

It works.

### Actual

```
2019-06-27 10:12:59.579419: [info] Cloning ab14502279c92084f06aa6222a17873275279e63 from https://github.com/shmish111/servant-purescript.git
2019-06-27 10:12:59.579589: [debug] Run process within /tmp/michael/with-repo11032: /run/current-system/sw/bin/git clone https://github.com/shmish111/servant-purescript.git cloned
2019-06-27 10:13:00.705248: [debug] Process finished in 1126ms: /run/current-system/sw/bin/git clone https://github.com/shmish111/servant-purescript.git cloned
2019-06-27 10:13:00.705527: [debug] Run process within /tmp/michael/with-repo11032/cloned: /run/current-system/sw/bin/git reset --hard ab14502279c92084f06aa6222a17873275279e63
2019-06-27 10:13:00.710885: [debug] Process finished in 5ms: /run/current-system/sw/bin/git reset --hard ab14502279c92084f06aa6222a17873275279e63
2019-06-27 10:13:00.711107: [debug] Run process within /tmp/michael/with-repo11032/cloned: /run/current-system/sw/bin/git submodule update --init --recursive
2019-06-27 10:13:00.749071: [debug] Process finished in 38ms: /run/current-system/sw/bin/git submodule update --init --recursive
2019-06-27 10:13:00.749315: [debug] Run process within /tmp/michael/with-repo11032/cloned: /run/current-system/sw/bin/git -c core.autocrlf=false archive -o /tmp/michael/with-repo-archive11032/foo.tar HEAD
2019-06-27 10:13:00.752674: [debug] Process finished in 3ms: /run/current-system/sw/bin/git -c core.autocrlf=false archive -o /tmp/michael/with-repo-archive11032/foo.tar HEAD
2019-06-27 10:13:00.752884: [debug] Run process within /tmp/michael/with-repo11032/cloned: /run/current-system/sw/bin/git submodule foreach --recursive "git -c core.autocrlf=false archive --prefix=$displaypath/ -o bar.tar HEAD && if [ -f bar.tar ]; then tar --force-local -Af /tmp/michael/with-repo-archive11032/foo.tar bar.tar ; fi"
2019-06-27 10:13:00.788258: [debug] Process finished in 35ms: /run/current-system/sw/bin/git submodule foreach --recursive "git -c core.autocrlf=false archive --prefix=$displaypath/ -o bar.tar HEAD && if [ -f bar.tar ]; then tar --force-local -Af /tmp/michael/with-repo-archive11032/foo.tar bar.tar ; fi"
2019-06-27 10:13:00.793175: [debug] parseArchive of GZIP-ed tar file: ZlibException (-3)
2019-06-27 10:13:00.794082: [error] Unsupported tarball from /tmp/michael/with-repo-archive11032/foo.tar: File located at "examples/central-counter/frontend/setupPath.sh" is a symbolic link to absolute path /home/robert/projects/gonimo-front/setupPath.sh
```

Inspecting the final error reveals a weirdness - that repository has a checked-in symlink to an absolute path on some person's computer!

Now, this is not a good idea, but it's still a valid Git repository and it used to work just fine. So I think this is a bug.

### Stack version

`2.1.1.1 x86_64 hpack-0.31.2`

### Method of installation

Nix.