DynamoRIO fails to run trivial "clone" example on ARM

Here's the program. It seems to work natively on several Linux architectures, and under DynamoRIO on Intel, but not under DynamoRIO on ARM, where I got a segfault in is_thread_tls_initialized.

The program puts a garbage value in the child's TLS pointer, which is hardly acceptable in a C program, so imagine this program written in assembler, if you prefer. If you're not using the standard libraries you're presumably free to use the TLS pointer however you like.

```
#define _GNU_SOURCE 1
#include
#include
#include

int child(void *arg)
{
_exit(0);
}

int main()
{
char *stack = malloc(4096);
int flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND |
CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS |
CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID);
void *arg = 0;
pid_t parent_tid = 0;
void *tls = (void *)0x123;
pid_t child_tid = 0;

clone(child, stack + 4096, flags, arg, &parent_tid, tls, &child_tid);
_exit(0);
}
```