Added 'jenkins' support directory to .gitignore

Signed-off-by: Erik de Bruin <erik@ixsoftware.nl>
Some minor modifications to the logic and more cleanup.

Signed-off-by: Erik de Bruin <erik@ixsoftware.nl>
- there is no 'sdk/generated' directory at this level: removed delete commands
- changed the 'wipe' target call on compiler.jx -which doesn't exist - to 'super-clean'

Signed-off-by: Erik de Bruin <erik@ixsoftware.nl>
We want the Jenkins job to always run as cleanly as possible so all aspects are tested and issues with third party downloads are not covered by the persistence of older artefacts.

Signed-off-by: Erik de Bruin <erik@ixsoftware.nl>