LeakSanitizer: detected memory leaks in delv

With gcc 8, the LeakSanitizer reports:

=================================================================
==20969==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 201 byte(s) in 1 object(s) allocated from:
    #0 0x7f260aecaed0 in malloc (/lib/x86_64-linux-gnu/libasan.so.5+0xe8ed0)
    #1 0x7f2608b4a08f in default_memalloc /builds/isc-private/bind9/lib/isc/mem.c:720

Indirect leak of 4189 byte(s) in 24 object(s) allocated from:
    #0 0x7f260aecaed0 in malloc (/lib/x86_64-linux-gnu/libasan.so.5+0xe8ed0)
    #1 0x7f2608b4a08f in default_memalloc /builds/isc-private/bind9/lib/isc/mem.c:720

SUMMARY: AddressSanitizer: 4390 byte(s) leaked in 25 allocation(s).

and the dnssec and mkeys tests fail: https://gitlab.isc.org/isc-private/bind9/-/jobs/99009

Both are using delv for the tests.