No longer works with latest glibc versions

Segfault on Ubuntu 20.04:

```
# gdb ./example -ex "run ./ulexec.so /usr/bin/cat /proc/self/maps"
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7ffe157 in ?? () from /lib64/ld-linux-x86-64.so.2
(gdb) bt
#0  0x00007ffff7ffe157 in ?? () from /lib64/ld-linux-x86-64.so.2
#1  0x0000000000000000 in ?? ()
```