required environment variables have no checks in all.bash

by **bear42**:

<pre>1. don't read all of the docs and just run ./all.bash like I did ;)

the attached patch adds some very basic error checking for the three
required environment vars</pre>


Attachments:
1. <a href="https://storage.googleapis.com/go-attachment/12/0/make.bash.patch">make.bash.patch</a> (1063 bytes)
