Fix #3746 (part 3): use correct PATH separator on Windows
Fix #3746 (part 3): use correct PATH separator on Windows

An IS-WINDOWS check would be too naive, because cygwin and git-bash use
: as the path separator, while powershell and cmd.exe use ;

hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d