Check for npm on path variable in NpmHelper on Windows

[nikolaia]

People on a team have npm in different locations, and the easiest way for the NpmHelpe to work out of the box would be to pick the location of the path-variable. It is painful to handle this manually when we have several projects.

In our projects we do it like this at the moment, but I could not get file globbing to work inside NpmHelper.fs:

System.Environment.GetEnvironmentVariable("PATH")
|> fun path -> path.Split ';'
|> Seq.append [ @"c:/programdata/scoop/apps/nodejs/"
                @"c:/program Files/nodejs/"
                @"c:/program Files (x86)/nodejs/"
                @"./packages/Npm.js/" ]
|> Seq.map (findToolInSubPath "npm.cmd")
|> Seq.tryFind fileExists
|> function
    | Some r -> r
    | None -> failwith "Unable to locate npm.cmd - if you have npm.cmd in a weird location you'll have to add it to the list in build.fsx. We tried looking in your PATH and some standard locations."

Some input would be greatly appreciated!

cc @mastoj

[forki]

thx