seawasp failing, maybe in glibc allocator

Hi,

Since seawasp's bleeding-edge clang moved to "20210226", it failed
every run except 4, and a couple of days ago it moved to "20210508"
and it's still broken.  It's always like this:

2021-05-09 03:31:37.602 CEST [1678796:171] pg_regress/_int LOG:
statement: RESET enable_seqscan;
corrupted double-linked list

... which doesn't appear in our code, but matches this:

https://github.com/bminor/glibc/blob/cedbf6d5f3f70ca911176de87d6e453eeab4b7a1/malloc/malloc.c#L1645

No reason to think it's our fault, but it'd be nice to see a
backtrace.  Is gdb installed, and are core files being dumped by that
SIGABRT, and are they using the default name
(/proc/sys/kernel/core_pattern = core), which the BF can find with the
value it's using, namely 'core_file_glob' => 'core*'?