sort: replace home made line reader by getline(3)

[bapt]

Summary

The previous code had bug when reading lines with an unexpected
encoding, returning without the full line being captured.
This result in sort complaining with "sort: Illegal byte sequence"

Using getline(3) instead of the home made code, fixes the situation.

PR: 241679

[imp]

usr.bin/sort/file.c

790

how is sort_opts_vals.zflag == 1 handled?

[bapt]

use getdelim(3) to be able to respect the -z flag

[markj]

Seems ok, I wrote a regression test case based on the PR. I'll commit it after this lands.

usr.bin/sort/file.c

78

Indentation is off.

788–797

I thought this would break -z, but I wrote a test case and it seems to work with this patch. I don't understand why.

[bapt]

Fix indentation

[imp]

usr.bin/sort/file.c

795

Do you need to do this when using the -z flag?

[bapt]

address @imp last comment

[markj]

usr.bin/sort/file.c

788–797