[gatsby] Fix production build hanging on createPagesStatefully

[nsimonson]

Fixes #3813

[nsimonson]

I'd say it'd be good to make sure the AppVeyor build finishes this time, but because of this bug they're queued up for days.

[KyleAMathews]

Deploy preview for using-glamor failed.

Built with commit be4fb97

https://app.netlify.com/sites/using-glamor/deploys/5a73dceedf99535000d2f472

[nsimonson]

🤔Seems like the netlify builds are still hanging

[gatsbybot]

Deploy preview for gatsbygram ready!

Built with commit be4fb97

https://deploy-preview-3816--gatsbygram.netlify.com

[Graham42]

If the globally installed version of gatsby is being used rather than the local one in node_modules will the Netlify builds ever work until we fix this bug?
I'm assuming (perhaps incorrectly) that Netlify auto-updates their environments to the latest version of gatsby. If so, this might mean the Netlify deploy with not work until this gets fixed. (ie. new version gets released)

[nsimonson]

@KyleAMathews Once this is released we should deprecate gatsby@1.9.176 and gatsby@1.9.177 for folks who may have already upgraded.

[nsimonson]

Closing in favor of 7bb93fe

[KyleAMathews]

Oops sorry! I should have merged this instead :-( I didn't look through PRs this morning before fixing the problem (I'd noticed it when working on something)