Description:
Even if the locale says that the first day of the week is Monday, 'cal' seems to ignore this information.

Package: util-linux 2.39-9
Config: Install en_DK.UTF-8 and en_US.UTF-8 locales

Steps to reproduce:
```
$ LC_TIME="en_DK.UTF-8" cal
June 2023
Su Mo Tu We Th Fr Sa
...
$ cal --version
cal from util-linux 2.39-dirty
```

Note that older version of 'cal' (restored from a backup) does not have the issue.
```
$ ./cal --version
cal from util-linux 2.38.1
$ LC_TIME="en_US.UTF-8" ./cal
June 2023
Su Mo Tu We Th Fr Sa
...
$ LC_TIME="en_DK.UTF-8" ./cal
June 2023
Mo Tu We Th Fr Sa Su
...
```

Suggestions/Ideas:
Upstream[1] does not seem to have modified code recently. Taking a look on the binary, it seems this part[2] of the sources is not present in the executable, suggesting that `HAVE_DECL__NL_TIME_WEEK_1STDAY` is not defined at compilation.

[1]: https://github.com/util-linux/util-linux/blob/master/misc-utils/cal.c
[2]: https://github.com/util-linux/util-linux/blob/master/misc-utils/cal.c#L362-L371