eclass/rpm: Sync with Gentoo

It's from Gentoo commit 26b30e180a4b2583452508d79ebb35d0e97fc696.

Signed-off-by: Flatcar Buildbot <buildbot@flatcar-linux.org>

sdk_container/src/third_party/portage-stable/eclass/rpm.eclass

@@ -1,4 +1,4 @@
-# Copyright 1999-2025 Gentoo Authors
+# Copyright 1999-2026 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 # @ECLASS: rpm.eclass
@@ -8,7 +8,7 @@
 # @BLURB: convenience class for extracting RPMs
 
 case ${EAPI} in
-	7|8) ;;
+	7|8) inherit eapi9-pipestatus ;;
 	*) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;;
 esac
 
@@ -17,7 +17,12 @@ _RPM_ECLASS=1
 
 inherit estack
 
-BDEPEND="app-arch/rpm2targz"
+BDEPEND="
+	|| (
+		app-arch/rpm2targz
+		>=app-arch/rpm-4.19.0
+	)
+"
 
 # @FUNCTION: rpm_unpack
 # @USAGE: <rpms>
@@ -37,8 +42,16 @@ rpm_unpack() {
 		else
 			a="${DISTDIR}/${a}"
 		fi
-		rpm2tar -O "${a}" | tar xf -
-		assert "failure unpacking ${a}"
+
+		if command -v rpm2tar >/dev/null; then
+			local extracttool=(rpm2tar -O)
+		else
+			# app-arch/rpm fallback
+			local extracttool=(rpm2archive -n)
+		fi
+
+		"${extracttool[@]}" "${a}" | tar xf -
+		pipestatus || die "failure unpacking ${a}"
 	done
 }