build: add v8 requirement to test-v8* in Makefile

The test targets expect that V8 is built in deps/v8/out

Ref: https://github.com/nodejs/node/issues/7477
PR-URL: https://github.com/nodejs/node/pull/7482


Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>