cmd/mbf: optionally build on early stages

This makes debugging the bootstrap process much less cumbersome.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/mbf/main.go

@@ -471,6 +471,9 @@ func main() {
 			flagExport  string
 			flagRemote  bool
 			flagNoReply bool
+
+			flagBoot bool
+			flagStd  bool
 		)
 		c.NewCommand(
 			"cure",
@@ -484,11 +487,18 @@ func main() {
 					return fmt.Errorf("unknown artifact %q", args[0])
 				}
 
+				t := rosa.Std
+				if flagBoot {
+					t -= 2
+				} else if flagStd {
+					t -= 1
+				}
+
 				switch {
 				default:
 					var pathname *check.Absolute
 					err := cm.Do(func(cache *pkg.Cache) (err error) {
-						pathname, _, err = cache.Cure(rosa.Std.Load(p))
+						pathname, _, err = cache.Cure(t.Load(p))
 						return
 					})
 					if err != nil {
@@ -541,7 +551,7 @@ func main() {
 					return cm.Do(func(cache *pkg.Cache) error {
 						return cache.EnterExec(
 							ctx,
-							rosa.Std.Load(p),
+							t.Load(p),
 							true, os.Stdin, os.Stdout, os.Stderr,
 							rosa.AbsSystem.Append("bin", "mksh"),
 							"sh",
@@ -553,7 +563,7 @@ func main() {
 					if flagNoReply {
 						flags |= remoteNoReply
 					}
-					a := rosa.Std.Load(p)
+					a := t.Load(p)
 					pathname, err := cureRemote(ctx, &addr, a, flags)
 					if !flagNoReply && err == nil {
 						log.Println(pathname)
@@ -591,6 +601,14 @@ func main() {
 			&flagNoReply,
 			"no-reply", command.BoolFlag(false),
 			"Do not receive a reply from the daemon",
+		).Flag(
+			&flagBoot,
+			"boot", command.BoolFlag(false),
+			"Build on the stage0 toolchain",
+		).Flag(
+			&flagStd,
+			"std", command.BoolFlag(false),
+			"Build on the intermediate toolchain",
 		)
 	}