[sdk-manage] Do not set a tools dir for i486 sb2 targets

Signed-off-by: Juha Kallioinen <juha.kallioinen@jollamobile.com>
[sdk-manage] Running under set -u so need to initialise

Signed-off-by: David Greaves <david.greaves@jollamobile.com>
[sdk-version] Update sdk-version file with Mer Repositories