ls: use libc::{major, minor} to calculate device number

[SteveLauC]

At the time of #2145, major and minor have not been added to libc, so we have to manually calculate the device number.

And those functions have been added (rust-lang/libc#2937) so that we can employ them.

BTW, I called cargo fmt on this file, but I didn't see rustfmt.toml in this project, so if you guys don't like it, feel free to ask to to discard the format changes.

Ref: #2140

[sylvestre]

I love simplifications :)

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/misc/timeout. tests/misc/timeout is passing on 'main'. Maybe you have to rebase?

[SteveLauC]

Test Android builds (28, default, x86) failed on a cp test, which seems unrelated to this PR:

failures:

---- test_cp::test_cp_parents_2_dirs stdout ----
current_directory_resolved: 
mkdir_all: /data/data/com.termux/files/usr/tmp/.tmp1DCT2X/a/b/c
mkdir: /data/data/com.termux/files/usr/tmp/.tmp1DCT2X/d
run: /data/data/com.termux/files/home/coreutils/target/debug/coreutils cp -a --parents a/b/c d
thread 'test_cp::test_cp_parents_2_dirs' panicked at 'Command was expected to succeed.
stdout = 
 stderr = cp: Permission denied (os error 13)
', tests/common/util.rs:176:9


failures:
    test_cp::test_cp_parents_2_dirs

test result: FAILED. 2325 passed; 1 failed; 31 ignored; 0 measured; 0 filtered out; finished in 215.43s

error: test failed, to rerun pass `--test tests`
error: 1 target failed:
    `--test tests`
Error: The process '/bin/sh' failed with exit code 101

And sadly I have no idea about the failure in Run GNU tests...

[sylvestre]

both of them aren't your fault ... noise :(

[sylvestre]

thanks!