fix: Ensure skip_if_unavailable=False for dnf/tdnf (#730)

Azure Linux 4.0 defaults to skip_if_unavailable=True, a change in
behavior from Azure Linux 3.0 and likely an inheritance from Fedora
upstream. It is important to ensure metadata is refreshed successfully
to ensure correctness of package install operations and to catch any
typos in user-provided repository configuration. Otherwise, the wrong
package versions might be silently installed.

Author: vinceaperri

toolkit/tools/pkg/imagecustomizerlib/customizepackages_rpm.go

@@ -275,7 +275,15 @@ func refreshRpmPackageMetadata(ctx context.Context, imageChroot *safechroot.Chro
 	_, span := startRefreshPackageMetadataSpan(ctx)
 	defer span.End()
 
-	args := []string{pmHandler.getVerbosityOption(), "check-update", "--refresh", "--assumeyes"}
+	// --setopt=skip_if_unavailable=False ensures failures to fetch repo metadata are fatal. TDNF already does this by
+	// default, but DNF on some distros (e.g. Azure Linux 4.0) defaults to skip_if_unavailable=True, so we set it
+	// explicitly for both. It is important to ensure metadata is refreshed successfully to ensure correctness of
+	// package install operations and to catch any typos in user-provided repository configuration. Otherwise, the wrong
+	// package versions might be silently installed.
+	args := []string{
+		pmHandler.getVerbosityOption(), "check-update", "--refresh", "--assumeyes",
+		"--setopt=skip_if_unavailable=False",
+	}
 
 	args = append(args, "--setopt=reposdir="+rpmsMountParentDirInChroot)