This depends on the format of the hosts file.

Executing twice the build.sh script results in the same ssh key reported twice in .ssh/authorized_keys in the remote server.
The build script should be idemptotent

build.sh builds both the server and the developer machine.
Two separate build scripts should exist

DRY!
The server IP number is stored twice in hosts and in build.sh

brew, apt-get and pip, used to install packages in local and remote hosts don't mention versions.
As noticed by @gimmi, this means that, virtually, different developers could end up with different packages versions.

After a default server setup, Apache is installed and running.
It should be removed

The script should be able to start from a brand new Mac.

Installing into a brand new server results in error, since pip is missing