internal/rosa: read-only access to built-ins

This removes potential footguns caused by mutable builtins without requiring unnecessary clones.

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

internal/rosa/rosa_test.go

@@ -28,7 +28,6 @@ var (
 )
 
 func TestMain(m *testing.M) {
-	rosa.Native().DropCaches("", rosa.OptLLVMNoLTO)
 	container.TryArgv0(nil)
 
 	code := m.Run()
@@ -79,8 +78,8 @@ func TestCureAll(t *testing.T) {
 	cache := getCache(t)
 	t.Parallel()
 
-	for _, p := range rosa.Native().CollectAll() {
-		_, a := rosa.Native().Std().MustLoad(p)
+	for _, p := range rosa.CollectAll() {
+		_, a := rosa.MustLoad(p)
 		t.Run(p.String(), func(t *testing.T) {
 			t.Parallel()
 
@@ -94,7 +93,7 @@ func TestCureAll(t *testing.T) {
 }
 
 func BenchmarkStage3(b *testing.B) {
-	t := rosa.Native().Clone().Std()
+	t := rosa.New().Std()
 
 	llvm := rosa.H("llvm")
 	for b.Loop() {