Odd 9.4, 9.3 buildfarm failure on s390x

Hi,

It seems Mark started a new buildfarm animal on s390x. It shows a pretty
odd failure on 9.3 and 9.4, but *not* on newer animals:

https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=lumpsucker&dt=2018-09-26%2020%3A30%3A58

================== pgsql.build/src/test/regress/regression.diffs ===================
*** /home/linux1/build-farm-8-clang/buildroot/REL9_4_STABLE/pgsql.build/src/test/regress/expected/uuid.out	Mon Sep 24 17:49:30 2018
--- /home/linux1/build-farm-8-clang/buildroot/REL9_4_STABLE/pgsql.build/src/test/regress/results/uuid.out	Wed Sep 26 16:31:31 2018
***************
*** 64,72 ****
  SELECT guid_field FROM guid1 ORDER BY guid_field DESC;
                guid_field
  --------------------------------------
-  3f3e3c3b-3a30-3938-3736-353433a2313e
-  22222222-2222-2222-2222-222222222222
   11111111-1111-1111-1111-111111111111
  (3 rows)

  -- = operator test
--- 64,72 ----
  SELECT guid_field FROM guid1 ORDER BY guid_field DESC;
                guid_field
  --------------------------------------
   11111111-1111-1111-1111-111111111111
+  22222222-2222-2222-2222-222222222222
+  3f3e3c3b-3a30-3938-3736-353433a2313e
  (3 rows)

  -- = operator test

======================================================================

Mark, is there anything odd for specific branches?

I don't see anything immediately suspicious in the relevant comparator
code...

Greetings,

Andres Freund