Make dagger version explicit.

Things built with 1.2.1 compiler won't run with the runtime library
from 1.2.0, so we need to ensure releases remain consistent.

Change-Id: Ie69349814cfce4c0d229be4372ce7210212a0497
Reviewed-on: http://gerrit.dmdirc.com/3230
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager