Revert "Figure out GOARM without being told (ref #1051)"

This reverts commit 2d7b0cf94d.

GOARM is not actually embedded and printed by "go env"

build.go

@@ -20,7 +20,6 @@ package main
 import (
 	"archive/tar"
 	"archive/zip"
-	"bufio"
 	"bytes"
 	"compress/gzip"
 	"flag"
@@ -76,18 +75,12 @@ func main() {
 	case "386", "amd64", "armv5", "armv6", "armv7":
 		break
 	case "arm":
-		// Grab GOARM from the environment
-		origGoArm := os.Getenv("GOARM")
-		if origGoArm == "" {
-			// Not found there, run "go env" to try to figure it out.
-			origGoArm = getGoEnv("GOARM")
-		}
-		switch origGoArm {
+		switch os.Getenv("GOARM") {
 		case "5", "6", "7":
-			goarch += "v" + origGoArm
+			goarch += "v" + os.Getenv("GOARM")
 			break
 		default:
-			log.Println("Invalid -goarch \"arm\". Use one of \"armv5\", \"armv6\", \"armv7\" or set GOARM.")
+			log.Println("Invalid goarch \"arm\". Use one of \"armv5\", \"armv6\", \"armv7\".")
 			log.Fatalln("Note that producing a correct \"armv5\" binary requires a rebuilt stdlib.")
 		}
 	default:
@@ -456,24 +449,6 @@ func runPipe(file, cmd string, args ...string) {
 	fd.Close()
 }
 
-func getGoEnv(key string) string {
-	bs, err := runError("go", "env")
-	if err != nil {
-		log.Fatal(err)
-	}
-	s := bufio.NewScanner(bytes.NewReader(bs))
-	for s.Scan() {
-		fields := strings.SplitN(s.Text(), "=", 2)
-		if len(fields) != 2 {
-			continue
-		}
-		if fields[0] == key {
-			return strings.Trim(fields[1], `"`)
-		}
-	}
-	return ""
-}
-
 type archiveFile struct {
 	src string
 	dst string