`spago -x` cannot parse Windows paths

[ozkutuk]

$ spago init
$ spago -x .\spago.dhall build
spago.exe:
Error: Invalid input

(input):1:4:
  |
1 | ./.\spago.dhall
  |    ^
unexpected '\'
expecting "", "", "", "", '/', ->, //, //\\, /\, :, end of input, keyword, operator, or whitespace

[f-f]

I suspect this is a duplicate of #472, where the bug is in this line? https://github.com/purescript/spago/blob/8ce19ea5648f8bd65d6db88428bac56e66cf2560/src/Spago/Config.hs#L115

I suspect that we can get around this by patching the path in Dhall's Options and calling inputExprWithOpts instead of inputExpr here

[f-f]

The new Spago does now allow for passing in alternate configuration files, so this does not apply anymore.