Seems like redundant env var separators (";" on Windows) in $PATH can
cause weird behavior. From #7377:
> After some time, system(['win32yank', '-o']) and system('win32yank -o')
> start returning different results: specifically first returns an
> empty string.
>
> 1. $PATH weirdly contains double semicolon followed by path to the
> “installation directory” (unpacked directory from archive).
> 2. If I run `let $PATH=substitute($PATH, ';;', ';', 'g')` the problem is fixed.
close#7377
ref 224f99b85d
59712f6dbe