Fixes firepit-builder pipeline on Windows

[abeisgoat]

Hi, welcome to PR, I'll bring around a round of waters to get you started.

Today's special is a series of artisan fixes from free-range developers.

First, we update the firepit-builder Dockerfile to use node@12, which has the decadent side-effect of shifting firepit builds to using node@12 as well. This is surely to delight your palette while keeping you hungry for more.

We're also thrilled to offer a flight of changes to firepit-builder/pipeline.js which compliment each other and come together into what we're calling Maintenant, le script de pipeline fonctionne sur Windows or (in English) "Now the pipeline script works on Windows." The largest issue was the config templating system used find/replace for paths, which did not handle Window's \ paths, as some of our patrons noticed that \ is an escape character in JSON, which produced a very conflicting flavor for some.

We're also thrilled to say, in the back kitchen, we've introduced the fame chef shx who will be helping us ensure that our chmod calls are cross-platform. Of course, he won't influence our primetime package.json menu and will stay as a core part of the firepit-builder section.

Aside from helping our Yelp reviews, we also believe that these updates should mend the issues raised in #1796 and hopefully stabilize the Windows builds by no longer corrupting the config files generated from our templates.

Thanks again for joining us tonight, I'll check back in a moment to get your orders.

[coveralls]

Coverage increased (+0.03%) to 65.603% when pulling 2b24c9e on ah-pipeline-win into 9ca80cf on master.

[samtstern]

Not opposed but was there any particular reason you made this update? Was something not working on 10?

[abeisgoat]

There's some issues with pkg with node@10 and by bumping to 12 we just sidestep that ordeal.

[samtstern]

Changes LGTM. And seems like you're having fun over there.