test: don't require specific GOARCH values.

This lets the test work for gccgo on other architectures.

R=r, rsc1
CC=golang-dev
https://golang.org/cl/4326044

test/env.go

@@ -6,7 +6,10 @@
 
 package main
 
-import os "os"
+import (
+	"os"
+	"runtime"
+)
 
 func main() {
 	ga, e0 := os.Getenverror("GOARCH")
@@ -14,8 +17,8 @@ func main() {
 		print("$GOARCH: ", e0.String(), "\n")
 		os.Exit(1)
 	}
-	if ga != "amd64" && ga != "386" && ga != "arm" {
-		print("$GOARCH=", ga, "\n")
+	if ga != runtime.GOARCH {
+		print("$GOARCH=", ga, "!= runtime.GOARCH=", runtime.GOARCH, "\n")
 		os.Exit(1)
 	}
 	xxx, e1 := os.Getenverror("DOES_NOT_EXIST")