Auto merge of #1878 - rupansh:master, r=JohnTitor

process_vm_readv, process_vm_writev should be available on android

process_vm_readv and process_vm_writev generally return -EPERM(-1) when used in android, however the syscalls work fine when running under privileged shell.
The following was tested(with modified nix) on Android 9/10 running Linux Kernel 4.9 on a SDM 845 phone:

```
fn read_mem_real(pid: i32, addr: usize, vsize: usize) -> Result<Vec<u8>, String> {
    let mut res = vec![0; vsize];
    let riovec: [RemoteIoVec; 1] = [RemoteIoVec {base: addr, len: vsize}];

    match process_vm_readv(Pid::from_raw(pid), &[IoVec::from_mut_slice(&mut res)], &riovec) {
        Err(e) => {
            log::info!("ERR {}", e);
            return Err(e.to_string());
        },
        Ok(_) => {
            return Ok(res);
        }
    }
}
```

This will work fine when run under su shell.