mkdir: fail if no arguments are provided

[andrewliebenow]

No description provided.

[andrewliebenow]

#6790 can be used instead of this for the no arguments fix, but we still need the fix in this PR for:

❯ /usr/bin/mkdir '' ; printf '%s\n' "${?:?}" 
/usr/bin/mkdir: cannot create directory ‘’: No such file or directory
1

❯ coreutils mkdir '' ; printf '%s\n' "${?:?}"
0

I'll update this PR accordingly when #6790 is merged.

[BenWiederhake]

I like this PR (and prefer it over #5790) because it emits a clearer error message, and also handles the case of emptystring-arguments.

However, the 10 CI failures make it unclear whether this breaks anything. Can you update to current main? This would include #6972, which should resolve some (all?) CI failures.

[andrewliebenow]

I had missed a "." in the test, fixed now