internal/rosa: create metadata alongside artifact

This enables deferring evaluation of azalea-based packages and fixes the longstanding quirk of version being disjoint from other metadata.

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

internal/rosa/libepoxy.go

@@ -21,9 +21,7 @@ func (t Toolchain) newLibepoxy() (pkg.Artifact, string) {
 	), version
 }
 func init() {
-	native.MustRegister(&Artifact{
-		f: Toolchain.newLibepoxy,
-
+	native.mustRegister(Toolchain.newLibepoxy, &Metadata{
 		Name:        "libepoxy",
 		Description: "a library for handling OpenGL function pointer management",
 		Website:     "https://github.com/anholt/libepoxy",