make build is broken for java 10

[carlosms]

This line in sbt does not work when the major version is 2 digits (e.g. 10).

gemini/sbt

Line 195 in d111064

echo "${version:2:1}"

[carlosms]

fixed for newer versions of the sbt script:
https://github.com/paulp/sbt-extras

[smola]

AFAIK Apache Spark does not work with Java 10 anyway, so this is likely to require upgrade to Apache Spark 2.4.0 and Scala 2.12.