Reading from STDIN fails when Debug logging is enabled.

Example program:

```rust
#[cfg(target_os = "hermit")]
use hermit as _;
use std::io;

fn main() {
println!("input please!");
let mut buffer = String::new();
if let Ok(_) = io::stdin().read_line(&mut buffer) {
print!("{}", buffer);
} else {
eprintln!("No input provided or an error occurred.");
}
}
```

compile (with `strace` feature enabled but makes no difference): `HERMIT_LOG_LEVEL_FILTER=Debug cargo build --target x86_64-unknown-hermit`

Output:
```
...
[0][INFO] Jumping into application
[0][DEBUG] Switching FPU owner from task 0 to 1
[0][WARN] Unable to read entropy! Fallback to a naive implementation!
sys_malloc(size = 1024, align = 1) = 0x400000011f80
sys_write(fd = 1, buf = 0x1d362dd, len = 14) = input please!
14
sys_malloc(size = 8192, align = 1) = 0x400000012400
sys_read(fd = 0, buf = 0x400000012400, len = 8192) = [0][DEBUG] Blocking task 1
[0][DEBUG] Only Idle Task is available.
[0][DEBUG] Switching task from 1 to 0 (stack 0x40000301DF60 => 0x11908)
```

Note, that `sys_read` doesn't return, so apparently, the debug prints lead to the read syscall to block.