dist/debian: force using jre-8 for ant
dist/debian: force using jre-8 for ant

On Ubuntu 14.04, apt installs jre-7 as /usr/bin/java default VM, we get compile
error on ant because of it.
To fix the error we need to change default VM to jre-8.

Fixes #17

Signed-off-by: Takuya ASADA <4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>
Message-Id: <1486968652-16807-1-git-send-email-4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>

scylladb/scylla-tools-java,scylladb/scylla-tools-java,scylladb/scylla-tools-java,scylladb/scylla-tools-java