Build is not failing on TypeScript errors

[Turbo87]

I would assume that running ember build would fail when I create a type error like changing the return type of normalizePath() to boolean instead of string.

I'm seeing the following output:

/route-recognizer.ts(633,7): Type 'boolean' is not assignable to type 'string'.
/route-recognizer/normalizer.ts(6,10): Type 'string' is not assignable to type 'boolean'.

but the build still succeeds with exit code 0.

/cc @stefanpenner @rwjblue @nathanhammond @krisselden

[Turbo87]

@stefanpenner @rwjblue @nathanhammond @krisselden any comments on this?

[rwjblue]

Yep. Fix it.

[chriskrycho]

Does adding noEmitOnError fix the problem? Seems to overlap in a weird way with noEmit, but that's the only thing I can think of which might help here.