Fix incorrect path normalization in coqdep on //..

`x/y//..` would get normalized to `x/y` instead of `x`

Fix coq#19862

tools/coqdep/lib/file_util.ml

@@ -23,7 +23,7 @@ let to_relative_path : string -> string = fun full_path ->
   List.fold_left add_parent path cwd
 
 let normalize_path : string -> string = fun path ->
-  let re_delim = if Sys.win32 then "[/\\]" else "/" in
+  let re_delim = if Sys.win32 then "[/\\]+" else "/+" in
   let path = Str.split_delim  (Str.regexp re_delim) path in
   let rec normalize acc path =
     match (path, acc) with