This also removes the need to have a test for `-b` parameter in
trigger-test-builds.sh, because the TC scripts calling this can already
factor that in.
Testing script trigger so only do builds of common to verify
Fixes: #14483
Test-bot: skip
Build-bot: skip:all build:common
Previously the builder scripts defined a readonly `VERSION` environment
variable for the Keyman version. That caused problems when another
(external) script tried to define a `VERSION` variable. We encountered
this problem when trying to move the TC build steps of a configuration
into a single script (#13399) when we tried to source `~/.nvm/nvm.sh`.
This change uses a Keyman specific prefix for the version variables and
renames `VERSION` → `KEYMAN_VERSION` etc. Unfortunately these variables
are used in a lot of places, so this turned out to be a bit of a yak
shave.
Test-bot: skip
- remove obsolete `packageName` variable
- add section on how to build with Docker, similar to how the
package build is done on GHA
- updated "uploading to Debian" section
- some reformatting
