rpm2cpio.sh: Improve error message

for unknown payload compression format. At this point it is unlikely
this isn't an RPM file as we detected the headers but much more likely
the package is using a newer compression format.

scripts/rpm2cpio.sh

@@ -60,5 +60,5 @@ case "$(_dd $offset bs=2 count=1 | tr -d '\0')" in
 	"$(printf '\375\067')") _dd $offset | xzcat   ;; # '\xfd\x37'
 	"$(printf '\135')") _dd $offset | unlzma      ;; # '\x5d\x00'
 	"$(printf '\050\265')") _dd $offset | unzstd  ;; # '\x28\xb5'
-	*) fatal "Unrecognized rpm file: $pkg" ;;
+	*) fatal "Unrecognized payload compression format in rpm file: $pkg" ;;
 esac