experimentalWatchApi is broken in 4.0

[MLoughry]

Expected Behaviour

ts-loader executes without crashing while experimentalWatchApi flag is set.

Actual Behaviour

Module build failed: RangeError: The normalization form should be one of NFC, NFD, NFKC, NFKD.
    at String.normalize (<anonymous>)
    at Object.directoryExists (d:\git\project\node_modules\ts-loader\dist\servicesHost.js:112:68)
    at Object.compilerHost.directoryExists (d:\git\project\node_modules\typescript\lib\typescript.js:77404:121)
    at d:\git\project\node_modules\typescript\lib\typescript.js:23409:22
    at Object.forEachAncestorDirectory (d:\git\project\node_modules\typescript\lib\typescript.js:11141:26)
    at getDefaultTypeRoots (d:\git\project\node_modules\typescript\lib\typescript.js:23407:12)
    at getEffectiveTypeRoots (d:\git\project\node_modules\typescript\lib\typescript.js:23393:20)
    at resolveTypeReferenceDirective (d:\git\project\node_modules\typescript\lib\typescript.js:23425:25)
    at resolveNamesWithLocalCache (d:\git\project\node_modules\typescript\lib\typescript.js:76752:38)
    at Object.resolveTypeReferenceDirectives (d:\git\project\node_modules\typescript\lib\typescript.js:76804:20)

Steps to Reproduce the Problem

Enable experimentalWatchApi.

The issue appears to be here, and repeated in the following few lines:

    directoryExists: path => compiler.sys.directoryExists(path.normalize(path)),

The parameter path is colliding with the import path from node.

I just tried turning this flag on as I was headed out of the office, so I'm not sure if there are other issues introduced in 4.0. I'll continue working on it tomorrow and/or next week.