Invalid argument OSError on practically every command
Installing 0.7.4 on Arch Linux using either the prebuilt binary or the curl method yields an `OSError` on practically every command:

Using curl:
```
$ curl https://nim-lang.org/choosenim/init.sh -sSf > init.sh
$ sh init.sh -y
choosenim-init: Downloading choosenim-0.7.4_linux_amd64
oserr.nim(94)            raiseOSError
Error: unhandled exception: Invalid argument
Additional info: "Try again" [OSError]

$ export CHOOSENIM_CHOOSE_VERSION=1.4.0
$ sh init.sh -y
choosenim-init: Downloading choosenim-0.7.4_linux_amd64
Downloading Nim 1.4.0 from nim-lang.org
oserr.nim(94)            raiseOSError
Error: unhandled exception: Invalid argument

$ export CHOOSENIM_CHOOSE_VERSION=1.0.8
$ sh init.sh -y
choosenim-init: Downloading choosenim-0.7.4_linux_amd64
Downloading Nim 1.0.8 from nim-lang.org
oserr.nim(94)            raiseOSError
Error: unhandled exception: Invalid argument
Additional info: "Try again" [OSError]
```
Using binary:
```
$ choosenim 1.4.0
choosenim 1.4.0
    Prompt: Can choosenim record and send anonymised telemetry data? [y/n]
        ... Anonymous aggregate user analytics allow us to prioritise
        ... fixes and features based on how, where and when people use Nim.
        ... For more details see: https://goo.gl/NzUEPf.
y
    Answer: Downloading Nim 1.4.0 from nim-lang.org
oserr.nim(94)            raiseOSError
Error: unhandled exception: Invalid argument
Additional info: "Try again" [OSError]

$ choosenim 1.0.8
Downloading Nim 1.0.8 from nim-lang.org
oserr.nim(94)            raiseOSError
Error: unhandled exception: Invalid argument
Additional info: "Try again" [OSError]

$ choosenim update stable
   Updating stable
oserr.nim(94)            raiseOSError
Error: unhandled exception: Invalid argument
Additional info: "Try again" [OSError]

$ choosenim versions
oserr.nim(94)            raiseOSError
Error: unhandled exception: Invalid argument
Additional info: "Try again" [OSError]
```

The only arguments that appear to work when passed to the binary are `--help` and `--version`.

I've also tried installing choosenim with nimble, but it fails to build (#239).

## Details
OS: Arch Linux 5.9.1
Nim: 1.4.0
Nimble: 0.11.0