Stop bundling libraries in release

- Instead we now use CentOS 7 for the static build to guarantee
  that we only depend on libc v2.17

- For macOS we now pull in a static node binary and bundle that instead.

doc/npm.md

@@ -20,7 +20,7 @@ sudo apt-get install -y \
 
 ```bash
 sudo yum groupinstall -y 'Development Tools'
-sudo yum config-manager --set-enabled PowerTools
+sudo yum config-manager --set-enabled PowerTools # unnecessary on CentOS 7
 sudo yum install -y python2 libsecret-devel libX11-devel libxkbfile-devel
 npm config set python python2
 ```