cmd/mbf: optionally register all targets

This enables non-native cures from the daemon.

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

internal/rosa/stage0.go

@@ -49,3 +49,12 @@ func init() {
 		Description: "Rosa OS stage0 bootstrap seed",
 	}
 }
+
+// HasStage0 returns whether a stage0 distribution is available.
+func HasStage0() (ok bool) {
+	func() {
+		defer func() { ok = recover() == nil }()
+		toolchainStage0.Load(stage0Dist)
+	}()
+	return
+}