id: rustix crate bypasses libc breaking LD_PRELOAD based tools

Problem

• https://github.com/uutils/coreutils/commit/37c42a29caa9f20a7d509cf59b9f3d177075aa5c replaced the nix crate with rustix for id.
• rustix uses raw syscalls for functions such as getuid(), rather than the libc wrapper.
• Tools like fakeroot rely on the libc wrapper to intercept function calls using LD_PRELOAD in order to return fake values.

Reproduce

1. Build uutils/coreutils version 0.9.0 using the release profile
2. Install fakeroot:

# Debian / Ubuntu 
sudo apt install fakeroot

# Fedora / RHEL
sudo dnf install fakeroot

# Arch Linux
sudo pacman -S fakeroot

3. Run the built id:

id

Output:

1000

4. Run fakeroot against the built id:

fakeroot ./target/release/coreutils id -u

Output:

1000

Expected behavior

fakeroot should be able to intercept the id command and instead print:

0

as if it were root.

Build uutils/coreutils 0.9.0 with the release profile and reproduce the issue using fakeroot ./target/release/coreutils id -u. Start by locating the id implementation and its rustix-based calls, then investigate how fakeroot intercepts the corresponding libc wrappers. Done means fakeroot causes id -u to print 0 instead of 1000.