`choosenim devel --latest` fails build
Hello,

I saw `choosenim devel --build` fail on a Travis CI run, and then was also able to reproduce that same issue on Windows 10.

[Here's the Travis failure](https://travis-ci.org/github/kaushalmodi/aoc2019/jobs/772325553).

```
... /home/travis/.choosenim/toolchains/nim-#devel/compiler/semtypes.nim(259, 78) Error: undeclared field: 'isNaN' for type system.BiggestFloat [declared in /home/travis/.choosenim/toolchains/nim-#devel/lib/system.nim(1397, 3)] 
... FAILURE
```