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/argp-standalone.go

@@ -26,9 +26,7 @@ install -D -m755 libargp.a /work/system/lib/libargp.a
 	), version
 }
 func init() {
-	native.MustRegister(&Artifact{
-		f: Toolchain.newArgpStandalone,
-
+	native.mustRegister(Toolchain.newArgpStandalone, &Metadata{
 		Name:        "argp-standalone",
 		Description: "hierarchical argument parsing library broken out from glibc",
 		Website:     "http://www.lysator.liu.se/~nisse/misc/",