cmd/bench: set runstamp for subrepo tests

For golang/go#53538.

Change-Id: Ic68861b65a7b5cd259ab6c8c82a10a08323f1a6d
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/459096
Auto-Submit: Michael Pratt <[email protected]>
Run-TryBot: Michael Pratt <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: David Chase <[email protected]>

Author: prattmic

cmd/bench/main.go

@@ -65,8 +65,6 @@ func toolchainFromGOROOT(name, goroot string) *toolchain {
 }
 
 func run(tcs []*toolchain) error {
-	fmt.Printf("runstamp: %s\n", time.Now().In(time.UTC).Format(time.RFC3339Nano))
-
 	// Because each of the functions below is responsible for running
 	// benchmarks under each toolchain itself, it is also responsible
 	// for ensuring that the benchmark tag "toolchain" is printed.
@@ -152,6 +150,8 @@ func main() {
 		subRepoBaseline = os.Getenv("BENCH_SUBREPO_BASELINE_PATH")
 	}
 
+	fmt.Printf("runstamp: %s\n", time.Now().In(time.UTC).Format(time.RFC3339Nano))
+
 	if repository != "go" {
 		toolchain := toolchainFromGOROOT("baseline", gorootBaseline)
 		if err := goTestSubrepo(toolchain, repository, subRepoBaseline, subRepoExperiment); err != nil {