As with the previous similar changes, this is intended to catch
problems as they happen instead of ignoring them and continuing on
to potentially fail later. Setting this on all existing scripts
will allow us to enforce use via Jenkins.
Change-Id: Iad2d490c86dceab148ea9ab08f457c49a5d5352e
In the bash script "99-override-default-apt-conf" 'set -u'
is being used to check for uninitialised variables.
This resulted in generic 'unbound variable' messages rather
than the intended error messages.
Tweaked the check for DIB_APT_CONF to work if the variable is unbound;
so that we get the intended error message rather than the `unbound
variable` message.
Change-Id: Ib8e287060f32312ab80dd7f44e2792ecca48edbb