internal/rosa/package: migrate toybox

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

internal/rosa/stage0.go

@@ -28,7 +28,7 @@ tar \
 `, pkg.Path(fhs.AbsRoot.Append("stage0"), false, t.Append(nil,
 			LLVM,
 			Mksh,
-			toyboxEarly,
+			_toyboxEarly,
 		)...))
 	})
 }
@@ -37,7 +37,7 @@ tar \
 func (s *S) HasStage0() (ok bool) {
 	func() {
 		defer func() { ok = recover() == nil }()
-		s.New(stageEarly).MustLoad(stage0Dist)
+		s.New(stageEarly).MustLoad(_stage0Dist)
 	}()
 	return
 }