Issue title: Can't build with OpenSSL 1.1 on Arch Linux
 Issue body: As discussed elsewhere with @fnichol, we haven't been able to build Habitat on Arch Linux for almost two months.

```
error: failed to run custom build command for `openssl v0.9.24`                                                                                                                                                                         
process didn't exit successfully: `/home/trevor/code/aur/habitat/src/habitat/target/debug/build/openssl-3a8db21765a1c7e0/build-script-build` (exit code: 101)
--- stderr
thread 'main' panicked at 'Unable to detect OpenSSL version', /home/trevor/code/aur/habitat/src/cargo-repository/registry/src/github.com-1ecc6299db9ec823/openssl-0.9.24/build.rs:16:14
note: Run with `RUST_BACKTRACE=1` for a backtrace.

warning: build failed, waiting for other jobs to finish...
error: build failed                                                                                                                                                                                                                     
make: *** [Makefile:178: build-hab] Error 101
==> ERROR: A failure occurred in build().
    Aborting... 
```

See: https://github.com/sfackler/rust-openssl/issues/994
 Comments: 
 Comment 0: @fnichol we are putting this in the backlog, please provide any input you may have
 Comment 1: Came here because I've been running into this as well for awhile. I've just removed habitat for now since I mostly installed it to play with it for a work project. The new error is simply:

```error: target not found: openssl<1.1.1```
 Comment 2: This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. We value your input and contribution. Please leave a comment if this issue still affects you.

{'source': 'GithubIssues', 'repo_name_with_owner': 'habitat-sh/habitat', 'issue_id': 378920062, 'repo_stars': 2585.0}