du: fix -l/--count-links option not counting hardlinks separately

[WaterWhisperer]

Fixes: #9871

Reproduce:

mkdir test && cd test
dd if=/dev/zero of=file1 bs=1k count=64 2>/dev/null
ln file1 file1.1
dd if=/dev/zero of=file2 bs=1k count=16 2>/dev/null

$ du .
84	.

$ du -l .
148

$ /bin/du .
84	.

$ /bin/du -l .
148

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/cp/cp-mv-enotsup-xattr. tests/cp/cp-mv-enotsup-xattr is passing on 'main'. Maybe you have to rebase?
Note: The gnu test tests/csplit/csplit-io-err was skipped on 'main' but is now failing.

[anastygnome]

Hey, could you add test code ?

[WaterWhisperer]

Hey, could you add test code ?

Sure

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/cp/cp-mv-enotsup-xattr. tests/cp/cp-mv-enotsup-xattr is passing on 'main'. Maybe you have to rebase?
Note: The gnu test tests/csplit/csplit-io-err was skipped on 'main' but is now failing.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

[sylvestre]

thanks