gs_group_1 crashing on 13beta2/s390x

On the Debian s390x buildd, the 13beta2 build is crashing:

2020-07-15 01:19:59.149 UTC [859] LOG:  server process (PID 1415) was terminated by signal 11: Segmentation fault
2020-07-15 01:19:59.149 UTC [859] DETAIL:  Failed process was running: create table gs_group_1 as
    select g100, g10, sum(g::numeric), count(*), max(g::text)
    from gs_data_1 group by cube (g1000, g100,g10);

Full build log at
https://buildd.debian.org/status/fetch.php?pkg=postgresql-13&arch=s390x&ver=13%7Ebeta2-1&stamp=1594776007&raw=0

The failure is reproducible there:
https://buildd.debian.org/status/logs.php?pkg=postgresql-13&ver=13%7Ebeta2-1&arch=s390x

I tried a manual build on a s390x machine, but that one went through
fine, so I can't provide a backtrace at the moment.

Christoph