cmd/coordinator, internal/buildgo: create buildgo package

This package contains the BuilderRev type moved from cmd/coordinator.

The rest of the CL is simply updating coordinator with the new
exported names of the type and its fields.

This refactoring is in preparation for moving the benchmark building and running
code into a separate package.

(Most of the diff could have been avoided with a type alias, but I
assume we'd rather not do that.)

Updates golang/go#19871

Change-Id: Ib6ce49431c8529d6b4e72725d3cd652b9d0160db
Reviewed-by: Brad Fitzpatrick <>
6 files changed