It fails on x86_64 with:
```
Use --max-threads=INT to specify a larger number of threads
and rerun valgrind
valgrind: the 'impossible' happened:
Max number of threads is too low
host stacktrace:
==174357== at 0x58042F5A: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==174357== by 0x58043087: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==174357== by 0x580432EF: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==174357== by 0x58043310: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==174357== by 0x58099E77: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==174357== by 0x580E67E9: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==174357== by 0x5809D59D: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==174357== by 0x5809901A: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==174357== by 0x5809B0B6: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==174357== by 0x580E4050: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
sched status:
running_tid=1
Thread 1: status = VgTs_Runnable syscall 56 (lwpid 174357)
==174357== at 0x4A07816: clone (in /usr/lib64/libc.so.6)
==174357== by 0x4A08720: __clone_internal (in /usr/lib64/libc.so.6)
==174357== by 0x4987ACF: create_thread (in /usr/lib64/libc.so.6)
==174357== by 0x49885F6: pthread_create@@GLIBC_2.34 (in /usr/lib64/libc.so.6)
==174357== by 0x1093B5: test.part.0 (lib3026.c:64)
==174357== by 0x492454F: (below main) (in /usr/lib64/libc.so.6)
client stack range: [0x1FFEFFC000 0x1FFF000FFF] client SP: 0x1FFEFFC998
valgrind stack range: [0x1002BAA000 0x1002CA9FFF] top usage: 11728 of 1048576
[...]
```
