UBUNTU: snapcraft.yaml: add dpkg-dev to the build deps

BugLink: http://bugs.launchpad.net/bugs/1718886Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

snapcraft.yaml

@@ -29,3 +29,4 @@ parts:
     build-packages:
       - cpio
       - libssl-dev
+      - dpkg-dev