Compile w/o using parent directory configs

[GoldtoothFour]

It builds using the `switch` configs in the parent dir's `config.nims`: if I 
run `nim c -r --app:bin --out:binary --skipParentCfg:on` in the `util` folder, 
it compiles a _library_ using the parent dir's `config.nims` and tries to run 
the resulting `*.so`. My project structure looks like:
    
    
    src
    |  pkgname
    |  |  util
    |  |  |  binary.nim
    |  |  config.nims
    |  |  ...
    |  pkgname.nim
    pkgname.nimble
    
    
    Run