Debian/Ubuntu instructions appear to be out of date

[mcandre]

The posted installation steps for manually installing the CloudABI toolchain with the cloudabi-run utility in Debian/Ubuntu, omits some important requirements:

• yaml2argdata headers need to be installed.
• arpc needs to be installed.
• The libyaml-cpp-dev package needs to be installed.
• python3 needs to be installed.
• pypeg2 needs to be installed.
• etc.

Without these steps, cloudabi-utils fails to compile. Many of these additional steps are documented in the Dockerfile, but have not been copied to the plain vanilla Debian/Ubuntu documentation.

Could we move these commands to a standalone shell script, and have both the Dockerfile and the documentation point to that, to keep everything in sync?