Downgrade Node from 8.12.0 back to 8.11.4, for now.

This minor update was evidently too risky to slip into a release candidate
of Meteor 1.7.1: https://github.com/meteor/meteor/issues/10216

You can still use Node 8.12.0 to run your app in production, and thus get
the benefits of https://github.com/meteor/meteor/pull/10090, even if it's
not the version used in development.

History.md

@@ -14,11 +14,6 @@ N/A
 
 ### Changes
 
-* Node has been updated to version
-  [8.12.0](https://nodejs.org/en/blog/release/v8.12.0/), which provides
-  [performance improvements](https://github.com/nodejs/node/pull/20727)
-  for `Fiber`-heavy Meteor applications, among many other benefits.
-
 * Meteor 1.7 introduced a new client bundle called `web.browser.legacy` in
   addition to the `web.browser` (modern) and `web.cordova` bundles.
   Naturally, this extra bundle increased client (re)build times. Since

scripts/build-dev-bundle-common.sh

@@ -5,7 +5,7 @@ set -u
 
 UNAME=$(uname)
 ARCH=$(uname -m)
-NODE_VERSION=8.12.0
+NODE_VERSION=8.11.4
 MONGO_VERSION_64BIT=4.0.2
 MONGO_VERSION_32BIT=3.2.19
 NPM_VERSION=6.4.1