fix(ec): normalize paths when matching ghost residue

Use filepath.Clean on both the freshly opened output file names and
the ghost paths so that lexically different but equivalent paths
(e.g. "./datadir/X.ec00" vs "datadir/X.ec00") still match. Without
this, a redundant entry in additionalDirs could let a ghost path slip
through the overwritten check and os.Remove a freshly rebuilt shard.

weed/storage/erasure_coding/ec_encoder.go

@@ -226,11 +226,11 @@ func generateMissingEcFiles(baseFileName string, bufferSize int, largeBlockSize
 	freshOutputs := make(map[string]struct{}, len(outputFiles))
 	for _, f := range outputFiles {
 		if f != nil {
-			freshOutputs[f.Name()] = struct{}{}
+			freshOutputs[filepath.Clean(f.Name())] = struct{}{}
 		}
 	}
 	for _, ghost := range ghostPaths {
-		if _, overwritten := freshOutputs[ghost]; overwritten {
+		if _, overwritten := freshOutputs[filepath.Clean(ghost)]; overwritten {
 			continue
 		}
 		if removeErr := os.Remove(ghost); removeErr != nil && !os.IsNotExist(removeErr) {