build: remove xgo cross-builds (#23800)

xgo is not maintained at this time, so none of these builds work.

Closes #23784

build/ci.go

@@ -33,7 +33,6 @@ Available commands are:
    nsis                                                                                        -- creates a Windows NSIS installer
    aar        [ -local ] [ -sign key-id ] [-deploy repo] [ -upload dest ]                      -- creates an Android archive
    xcode      [ -local ] [ -sign key-id ] [-deploy repo] [ -upload dest ]                      -- creates an iOS XCode framework
-   xgo        [ -alltools ] [ options ]                                                        -- cross builds according to options
    purge      [ -store blobstore ] [ -days threshold ]                                         -- purges old archives from the blobstore
 
 For all commands, -n prevents execution of external programs (dry run mode).
@@ -188,8 +187,6 @@ func main() {
 		doAndroidArchive(os.Args[2:])
 	case "xcode":
 		doXCodeFramework(os.Args[2:])
-	case "xgo":
-		doXgo(os.Args[2:])
 	case "purge":
 		doPurge(os.Args[2:])
 	default:
@@ -1209,48 +1206,6 @@ func newPodMetadata(env build.Environment, archive string) podMetadata {
 	}
 }
 
-// Cross compilation
-
-func doXgo(cmdline []string) {
-	var (
-		alltools = flag.Bool("alltools", false, `Flag whether we're building all known tools, or only on in particular`)
-	)
-	flag.CommandLine.Parse(cmdline)
-	env := build.Env()
-	var tc build.GoToolchain
-
-	// Make sure xgo is available for cross compilation
-	build.MustRun(tc.Install(GOBIN, "github.com/karalabe/xgo@latest"))
-
-	// If all tools building is requested, build everything the builder wants
-	args := append(buildFlags(env), flag.Args()...)
-
-	if *alltools {
-		args = append(args, []string{"--dest", GOBIN}...)
-		for _, res := range allToolsArchiveFiles {
-			if strings.HasPrefix(res, GOBIN) {
-				// Binary tool found, cross build it explicitly
-				args = append(args, "./"+filepath.Join("cmd", filepath.Base(res)))
-				build.MustRun(xgoTool(args))
-				args = args[:len(args)-1]
-			}
-		}
-		return
-	}
-
-	// Otherwise execute the explicit cross compilation
-	path := args[len(args)-1]
-	args = append(args[:len(args)-1], []string{"--dest", GOBIN, path}...)
-	build.MustRun(xgoTool(args))
-}
-
-func xgoTool(args []string) *exec.Cmd {
-	cmd := exec.Command(filepath.Join(GOBIN, "xgo"), args...)
-	cmd.Env = os.Environ()
-	cmd.Env = append(cmd.Env, []string{"GOBIN=" + GOBIN}...)
-	return cmd
-}
-
 // Binary distribution cleanups
 
 func doPurge(cmdline []string) {