lib/libc: fix bug in parsing in getopt

[Kintaro]

getopt had an issue when parsing optional arguments if they had a space between the opion and its value.

Request: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=291374

Tested with bricoler run freebsd-src-regression-suite

[github-actions]

Thank you for taking the time to contribute to FreeBSD!
All issues resolved.

[Kintaro]

This probably needs to be backported, but as this is my first contribution I am not sure about the proper workflow on this._

[jlduran]

It should manually pass the following three tests (at least):

$ ./getoptest -l -w -d14 -s /usr/local/admin/tftproot -u admin -U 0
ch is l optarg is  NULL
ch is w optarg is  NULL
ch is d optarg is 14
ch is s optarg is /usr/local/admin/tftproot
ch is u optarg is admin
ch is U optarg is 0

$ ./getoptest -l -w -d 14 -s /usr/local/admin/tftproot -u admin -U 0
ch is l optarg is  NULL
ch is w optarg is  NULL
ch is d optarg is 14 # XXX <- (Or is it NULL? I'll have to test on Linux)
ch is s optarg is /usr/local/admin/tftproot
ch is u optarg is admin
ch is U optarg is 0

and

$ ./getoptest -l -w -d -s /usr/local/admin/tftproot -u admin -U 0
ch is l optarg is  NULL
ch is w optarg is  NULL
ch is d optarg is  NULL
ch is s optarg is /usr/local/admin/tftproot
ch is u optarg is admin
ch is U optarg is 0

[jlduran]

The style(9) fixes I was referring to in the bug report should be addressed, maybe using NetBSD style guide (https://cvsweb.netbsd.org/bsdweb.cgi/src/share/misc/style?rev=HEAD&content-type=text/x-cvsweb-markup).
Basically, use tabs, not spaces for indentation, and braces around single-line bodies are optional.

[Kintaro]

Thanks for the review. I fixed the tabs. Not sure on the braces. It is a "single instruction" but it is another nested if/else. Not contesting any of it, just unsure which one would be preferred.

As for the tests:

rootnode@x220 ~/c/c/291374> ./getopttest -l -w -d14 -s /usr/local/admin/tftproot -u admin -U 0
ch is l optarg is  NULL
ch is w optarg is  NULL
ch is d optarg is 14
ch is s optarg is /usr/local/admin/tftproot
ch is u optarg is admin
ch is U optarg is 0

rootnode@x220 ~/c/c/291374> ./getopttest -l -w -d 14 -s /usr/local/admin/tftproot -u admin -U 0
ch is l optarg is  NULL
ch is w optarg is  NULL
ch is d optarg is 14
ch is s optarg is /usr/local/admin/tftproot
ch is u optarg is admin
ch is U optarg is 0

rootnode@x220 ~/c/c/291374> ./getopttest -l -w -d -s /usr/local/admin/tftproot -u admin -U 0
ch is l optarg is  NULL
ch is w optarg is  NULL
ch is d optarg is  NULL
ch is s optarg is /usr/local/admin/tftproot
ch is u optarg is admin
ch is U optarg is 0