sweet: only enable gvisor benchmark by default for amd64

Currently this benchmark suite only run on amd64. This CL removes it
from the default benchmarks for other architectures, so that "sweet run"
can pass by default.

This CL also adds a prerequisite check for amd64, so that it can report
errors in advance.

Fixes golang/go#67869

Change-Id: I0454d5557bb0587c1c0314a42b02bf88105a2fe4
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/601075
Reviewed-by: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Austin Clements <austin@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: hliu-ampere

sweet/cmd/sweet/benchmark.go

@@ -105,10 +105,14 @@ var benchmarkGroups = func() map[string][]*benchmark {
 		allBenchmarksMap["etcd"],
 		allBenchmarksMap["go-build"],
 		allBenchmarksMap["gopher-lua"],
-		allBenchmarksMap["gvisor"],
+	}
+	if runtime.GOARCH == "amd64" {
+		m["default"] = append(m["default"], allBenchmarksMap["gvisor"])
+	}
+	m["default"] = append(m["default"],
 		allBenchmarksMap["markdown"],
 		allBenchmarksMap["tile38"],
-	}
+	)
 
 	for i := range allBenchmarks {
 		m["all"] = append(m["all"], &allBenchmarks[i])

sweet/harnesses/gvisor.go

@@ -21,6 +21,9 @@ func (h GVisor) CheckPrerequisites() error {
 	if runtime.GOOS != "linux" {
 		return fmt.Errorf("requires Linux")
 	}
+	if runtime.GOARCH != "amd64" {
+		return fmt.Errorf("requires amd64")
+	}
 	return nil
 }