Fix build util paths for Windows

[vidartf]

References

Fixes build utils for Windows after #6034.

Also ensures that file contents line endings are normalized, to prevent line-ending only diffs.

Code changes

Replaces path sep with '/' to normalize slashes.

Replaces '\n' with the current line ending of the file in ensureFile.

User-facing changes

None

Backwards-incompatible changes

None

[jupyterlab-dev-mode]

Thanks for making a pull request to JupyterLab!

To try out this branch on binder, follow this link:

[blink1073]

LGTM, thanks!

[jasongrout]

Should we backport this?

[blink1073]

Sure, why not.

[blink1073]

@meeseeksdev backport to 1.0.x

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

$ git checkout 1.0.x
$ git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

$ git cherry-pick -m1 bef72f15217d9a5fff7a47f2a690fe13e1309da2

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

$ git commit -am 'Backport PR #7019: Fix build util paths for Windows'

4. Push to a named branch :

git push YOURFORK 1.0.x:auto-backport-of-pr-7019-on-1.0.x

5. Create a PR against branch 1.0.x, I would have named this PR:

"Backport PR #7019 on branch 1.0.x"

And apply the correct labels and milestones.

Congratulation you did some good work ! Hopefully your backport PR will be tested by the continuous integration and merged soon!

If these instruction are inaccurate, feel free to suggest an improvement.

[blink1073]

nvm, not worth doing manually

[vidartf]

Cleaned up the label.