Add readme for build spidermonkey60

[jiangphcn]

Overview

Add readme for building spidermonkey60 in Windows

Related Issues or Pull Requests

apache/couchdb#2170

[wohali]

@jiangphcn I ran out of time today but this is on my agenda for tomorrow.

[wohali]

@jiangphcn Hi Peng, thanks so much for this work. Clearly this took you a lot of time, and my own experiences are similar with how painstaking it can be.

There's still a bunch to do to make this useful for end users, as the instructions aren't yet step-by-step for everything. For me to use this to automate Windows builds I need full repeatable steps, in the same order along with everything else we build.

I'm going to suggest we leave this on the build-spidermonkey60 branch for now, until we can fully update README.md for SpiderMonkey 60. That means we'd close this PR but you should keep the branch and NOT delete it, this is extremely valuable information.

Thank you again for all your hard work! 🍾

[jiangphcn]

THANKS so much for your nice words @wohali. Yes, it is enough painful to get it finally working :-) Again, yes, there are some manual work on that with the steps in this PR. I can work or co-work to make it automate enough, given that this is must. Hope this is not blocking CouchDB 3.0, but want to check how far we can go with non-windows version for CouchDB 3.0.