Migrate to build.sbt

[hawkw]

According to the sbt documentation,

sbt 0.13’s introduction of multi-project build.sbt made the Build trait redundant. In addition, the auto plugin feature that’s now standard in sbt 0.13 enabled automatic sorting of plugin settings and auto import feature, but it made Build.scala more difficult to maintain.

In sbt 0.13.13, using the Build trait for build definitions has been deprecated, and it will be removed when sbt 1.0 is released. Therefore, we will want to move to using a build.sbt-based build definition before the release of sbt 1.0.

[hawkw]

Note that the documentation does state that although using the Build trait for the build definition is deprecated,

you can still use project/*.scala file to organize your build and/or define ad-hoc plugins

So this won't require a complete restructuring of our build definition. We will just need to rewrite LinkerdBuild.scala as build.sbt.

[hawkw]

Since sbt 1.0.0 was released 12 days ago, I'd really like to get this done before we release Linkerd 1.2.0.