README for Linux missing information

[supercooldave]

One of the (new) students followed through the README file to build encore on linux. After completing the (brief) instructions, she didn't have a working Encore compiler. By simply typing make, one was quickly available, but the instructions did not say that. I noticed that sh debian-install.sh build, or something like that, would also have done the trick.

Apparently, it would be useful to state which stack to install. Be more specific.

Could someone make the appropriate fix?