Build error due to discarded-qualifiers

I'm trying to build 864b432cd7bf8218289a14131e2bde817609e6d0 with gcc 15 (sic!), Arch-based repo, bare metal. There is an error caused by https://github.com/aws/aws-lc/pull/3291/changes

```
In file included from ./aws-lc/crypto/rand_extra/urandom.c:70:
./aws-lc/crypto/rand_extra/../internal.h: In function 'OPENSSL_memchr':
./aws-lc/crypto/rand_extra/../internal.h:939:10: error: return discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
939 | return memchr(s, c, n);
| ^~~~~~
```

see https://github.com/hnakamur/aws-lc/blob/9978a847da19c1e3a471e26c8778bc83ffcfcf86/crypto/internal.h#L942

PS: Sorry, my fault. A full checkout on a sparse checkout does not update.