cmd/go: remove the bootstrap with make.bash error message

The runtime/zgoos_$GOOS.go and runtime/zgoarch_$GOARCH.go files
are in the repository now, so the message is actually incorrect
(running make.bash won't generate those). The reason is probably
wrong $GOROOT.

Change-Id: I8dc125594c52d666eca91fd5af48b60d12d599b8
Reviewed-on: https://go-review.googlesource.com/15221
Reviewed-by: Ian Lance Taylor <[email protected]>

src/cmd/go/build.go

@@ -1235,12 +1235,6 @@ func (b *builder) build(a *action) (err error) {
 		fmt.Fprintf(os.Stderr, "%s\n", a.p.ImportPath)
 	}
 
-	if a.p.Standard && a.p.ImportPath == "runtime" && buildContext.Compiler == "gc" &&
-		(!hasString(a.p.GoFiles, "zgoos_"+buildContext.GOOS+".go") ||
-			!hasString(a.p.GoFiles, "zgoarch_"+buildContext.GOARCH+".go")) {
-		return fmt.Errorf("%s/%s must be bootstrapped using make%v", buildContext.GOOS, buildContext.GOARCH, defaultSuffix())
-	}
-
 	// Make build directory.
 	obj := a.objdir
 	if err := b.mkdir(obj); err != nil {
@@ -3355,16 +3349,3 @@ func raceInit() {
 	buildContext.InstallSuffix += "race"
 	buildContext.BuildTags = append(buildContext.BuildTags, "race")
 }
-
-// defaultSuffix returns file extension used for command files in
-// current os environment.
-func defaultSuffix() string {
-	switch runtime.GOOS {
-	case "windows":
-		return ".bat"
-	case "plan9":
-		return ".rc"
-	default:
-		return ".bash"
-	}
-}