internal/rosa: helpers for common url formats

This cleans up call site of NewPackage.

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

internal/rosa/pkg-config.go

@@ -7,11 +7,11 @@ func (t Toolchain) newPkgConfig() (pkg.Artifact, string) {
 		version  = "0.29.2"
 		checksum = "6UsGqEMA8EER_5b9N0b32UCqiRy39B6_RnPfvuslWhtFV1qYD4DfS10crGZN_TP2"
 	)
-	return t.NewPackage("pkg-config", version, pkg.NewHTTPGetTar(
-		nil, "https://gitlab.freedesktop.org/pkg-config/pkg-config/-/archive"+
-			"/pkg-config-"+version+"/pkg-config-pkg-config-"+version+".tar.bz2",
-		mustDecode(checksum),
-		pkg.TarBzip2,
+	return t.NewPackage("pkg-config", version, newFromGitLab(
+		"gitlab.freedesktop.org",
+		"pkg-config/pkg-config",
+		"pkg-config-"+version,
+		checksum,
 	), nil, &MakeHelper{
 		Generate: "./autogen.sh --no-configure",
 		Configure: []KV{