Incorrect sourcemap paths on Windows

[ArmorDarks]

There was an issue with JSPM jspm/jspm#2361, which later was resolved by #837.

Unfortunately, similar issue with sourcemaps paths still persists on Windows (assuming that mentioned fix has been already tested on non-Windows OS).

Here is example of sourcemap path on Windows 10:

{"version":3,"sources":["src/file:/J:/_DEL_JSPM_TEST/src/app.js"],"names":[],"mappings":";;;;;;AAAA,QAAQ","file":"build.js"}

To avoid duplication, I will refer to my comments in jspm/jspm#2361.

Starting from jspm/jspm#2361 (comment) I'm describing a case (there also can be found archive where the issue can be reproduced). In the last comment, I'm trying to dig to the reasons of that issue, with minor success, though.

[guybedford]

Sorry for the delayed response here. If you are able to track this down at all or provide a fix I'll gladly review.

[ArmorDarks]

That's jspm/jspm#2361 (comment) as far as I could track the issue. Afterward starts things, which I can't comprehend right now. I have a feeling that issue actually caused by Rollup.

[ArmorDarks]

The issue seems to be resolved in 0.17.0-beta.48. I suppose by updating Rollup dependency.

However, it introduced another issue #849