Add Windows iconv conversion

autoload/ale.vim

@@ -275,6 +275,18 @@ function! ale#GetLocItemMessage(item, format_string) abort
     " Windows may insert carriage return line endings (^M), strip these characters.
     let l:msg = substitute(l:msg, '\r', '', 'g')
 
+    if has('win32')
+        let l:to = &encoding
+
+        if l:to is# 'utf-8'
+            let l:res = iconv(l:msg, 'default', l:to)
+
+            if l:res isnot# '' && stridx(l:res, '?') == -1
+                let l:msg=l:res
+            endif
+        endif
+    endif
+
     return l:msg
 endfunction