Cutechess throws syscall errors on large books under unknown situations

[AndyGrant]

Indexing opening suite...
==746747== Thread 2 GameThread:
==746747== Syscall param waitid(infop) points to unaddressable byte(s)
==746747==    at 0x824274: ??? (in /home/andrew/Working/OpenBench/Client/cutechess-ob)
==746747==    by 0x495DC4B: ???
==746747==    by 0x2F: ???
==746747==    by 0x485848F: ???
==746747==    by 0x485844F: ???
==746747==    by 0x84B57F: ??? (in /home/andrew/Working/OpenBench/Client/cutechess-ob)
==746747==    by 0x2: ???
==746747==    by 0x7FFFFFFE: ???
==746747==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
==746747==

likely will not fix. And assume that Fastchess resolves. But noting in the interim.