ASSERT: unix/os.c:8838 iter->end <= sizeof(iter->buf)

This is with the current HEAD on git (commit 567cf5ac8d7a1830a99f86c17c556214a9aa270f) on Debian unstable, amd64:

```
$ cmake -DDEBUG=ON ..
$ make
$ bin64/drrun -- echo hello
end <= sizeof(iter->buf)
(Error occurred @0 frags)
version 6.0.16828, custom build
-no_dynamic_options -code_api -stack_size 56K -max_elide_jmp 0 -max_elide_call 0 -early_inject -emulate_brk -no_inline_ignored_syscalls -native_exec_default_list '' -no_native_exec_managed_code -no_indcall2direct
0x00007ffe7597b1c0 0x0000000071116876
0x00007ffe7597b320 0x00000000712e491a
0x00007ffe7597b340 0x00000000712d5460
0x00007ffe7597b790 0x0000000071118c58
0x00007ffe7597b7a0 0x000000007108f487
0x00007ffe7597bfd0 0x00000000712ff8ed
0x00007ffe7597ca00 0x00000000712b7427>
```

It works without the DEBUG:

```
$ cmake ..
$ make
$ bin64/drrun -- echo hello
hello
$
```

Is this a known issue, or am I doing something wrong?