win: provider: Detect(): return *.cmd path (#7577)

neovim-ruby-host is a ruby script.
neovim-node-host is a shell script.
Both don't work in cmd.exe so gem and npm provide batchfile shims.

Return the full path of these shims, cmd.exe knows better what to do with these files.

runtime/autoload/provider/ruby.vim

@@ -19,7 +19,7 @@ function! provider#ruby#Detect() abort
   if exists("g:ruby_host_prog")
     return g:ruby_host_prog
   else
-    return exepath('neovim-ruby-host')
+    return has('win32') ? exepath('neovim-ruby-host.cmd') : exepath('neovim-ruby-host')
   end
 endfunction