cmd/bench: add benchmark wrapper

The coordinator is getting support for running the benchmarks in this
repository. Since the benchmarks and interface are in flux, encoding all
of the details of running Go tests, bent arguments, etc into the
coordinator will likely cause churn and frustrating migration issues.

Instead, add cmd/bench which serves as the simple entrypoint for the
coordinator. The coordinator runs cmd/bench with the GOROOT to test
(eventually multiple GOROOTs), and this binary takes care of the
remaining details.

Right now, we just do a basic go test golang.org/x/benchmarks/... and
simple invocation of bent. Note that bent does not pass without
https://golang.org/cl/354634.

For golang/go#49207

Change-Id: I5c9cf89540cab605c0a64e17af85311d37985c25
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/359854
Trust: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
3 files changed