cmd/release: add new program to build releases

The release command will replace misc/makerelease from the main repo.
The contents of makerelease make their way into this program.

Also add GorootFinal and MakeScript methods to dashboard.BuildConfig.

Change-Id: Id20f3f7a85a21f040d8cf47e438d299d57360556
Reviewed-on: https://go-review.googlesource.com/3693
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
2 files changed