Comment 4 for bug 1935856

Add-on: I checked the sources provided at https://download.virtualbox.org/virtualbox/6.1.22/ and I think the responsible code snippet is in VirtualBox-6.1.22/src/VBox/HostDrivers/Support/SUPR3HardenedMain.cpp

```
$ cat -n VirtualBox-6.1.22/src/VBox/HostDrivers/Support/SUPR3HardenedMain.cpp | grep -A 10 2550
  2550 /*
  2551 * Check that we're root, if we aren't then the installation is butchered.
  2552 */
  2553 g_uid = getuid();
  2554 g_gid = getgid();
  2555 if (geteuid() != 0 /* root */)
  2556 supR3HardenedFatalMsg("SUPR3HardenedMain", kSupInitOp_RootCheck, VERR_PERMISSION_DENIED,
  2557 "Effective UID is not root (euid=%d egid=%d uid=%d gid=%d)",
  2558 geteuid(), getegid(), g_uid, g_gid);
  2559 #endif /* SUP_HARDENED_SUID */
  2560
```

When making a small demo:
```
$ cat a.c
#include <stdio.h>
#include <fcntl.h>

#include <unistd.h>
#include <sys/types.h>

int main(int argc, char** argv) {

    printf("Real user id: %d\n", getuid());
    printf("Effective user id: %d\n", geteuid());

    int res = openat(AT_FDCWD, "/dev/vboxnetctl", O_RDWR);

    if (res == -1) {
        perror(NULL);
        return 1;
    }
    printf("Opened file.\n");
    return 0;
}
```
with

```
$ gcc a.c
$ sudo chown root: a.out
$ ls -l a.out
-rwxrwxr-x 1 root root 16312 Jul 30 12:05 a.out

$ ./a.out
Real user id: 1000
Effective user id: 1000
Operation not permitted

$ sudo ./a.out
Real user id: 0
Effective user id: 0
Opened file.

$ sudo chmod u+s a.out
$ ./a.out
Real user id: 1000
Effective user id: 0
Opened file.
```

However, regardless if I provide each and every executable in /usr/lib/virtualbox/* the sticky bit with `chmod u+s` this error keeps popping up.

X11 showing the error dialog refers to /usr/lib/virtualbox/VBoxManage. But it seems very resilient to any of my attempts.

BUT: running VBoxManage as root (e.g. `sudo VirtualBox`) works like charm.