internal/rosa: remove external toolchain reference

This should have used toolchain passed as the argument and was mistakenly never changed when migrating to late evaluation.

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

internal/rosa/state.go

@@ -1132,7 +1132,7 @@ func (s *S) RegisterAzalea(r io.Reader, b fs.FS) error {
 		if !s.Register(string(f.Ident), func(t Toolchain) (*Metadata, pkg.Artifact) {
 			v, set, err := azalea.Evaluate[cachedArtifact](
 				(&evalContext{b, f, t}).pf,
-				s.getStack(),
+				t.getStack(),
 				*f,
 			)
 			if err != nil {