Blocked by #27570 (comment)

Unblocked by ampproject/amp-closure-compiler#23 and #29903

This PR has sat around for more than a month while I've battled with various parts of the compilation toolchain. At long last, we have a fully working minified build on Windows, and fully working unit and integration tests on Edge.

I'm sending this out for review so we can merge a blocking check for compilation on Windows and tests on Edge, and deal with IE test failures via a separate PR. Meanwhile, the current status on IE can be found in the PR description. (/cc @choumx)

/cc @samouri who is looking to use this on a windows workstation. (Please check out this branch and let me know how it works for you.)

I am not on a Windows machine so would defer to someone who can take a look under Windows.

I've tested this PR on a Windows VM that I installed on my personal Mac computer. Based on that, and on multiple green Windows runs on GH Actions, I'm going to merge this. Happy to address other Windows inconsistencies / bugs in follow up PRs.

We ran into gulp issues when trying to implement https://github.com/ampproject/amp.dev on WSL (Win 10). Will try again next week. Our fallback is to use a Mac (a supported OS); but WSL is preferred.

@jaygray0919: can you open up an issue on the amp.dev repo? This issue is only about the amphtml one.

FWIW, here are some items I've noticed about windows dev in the past week:

1. The babel unit tests break on windows
2. Things break when trying to use both WSL and regular Windows within the same folder, I have two clones of the repo to avoid weird compat issues.
3. The Karma tests don't work within WSL (at least not without manually setting CHROME_BIN env var, but still I ran in to issues), but work perfectly when I run them in regular windows
4. Windows Terminal is pretty nice :)