I saw such paragraph in MariaDB documentation and thought it may be useful.

Fixes #1076

- add missing TIMEOUT setup in other_OSes.yml,
- remove redundant code,
- cleanup comments and vars,
- use github.workspace var to set host workdir,
- get rid of old travis gitignore entry.

It seems redundant to keep these options and it complicates
which files are required by which containers. Installing all source
files should not cause any issue as long as they won't be used.

fixes: #955

- update comments,
- update RELEASE_STEPS.md,
- remove unused code and variables.