driver: print benchmark labels

Change-Id: Ic4ba5d4cfa67a84f0dd479ede1ace1ee965d85c7
Reviewed-on: https://go-review.googlesource.com/39491
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/driver/driver.go b/driver/driver.go
index 86f6382..b1fb3ad 100644
--- a/driver/driver.go
+++ b/driver/driver.go
@@ -66,6 +66,9 @@
 		return
 	}
 
+	fmt.Print("pkg: golang.org/x/benchmarks\n")
+	fmt.Printf("goos: %s\ngoarch: %s\n\n", runtime.GOOS, runtime.GOARCH)
+
 	stopTrace := startTrace()
 	defer stopTrace()