fix GOOS

weed/mount/unmount/unmount_std.go

@@ -1,5 +1,5 @@
-//go:build !linux
-// +build !linux
+//go:build !linux && !windows
+// +build !linux,!windows
 
 package unmount
 

weed/mount/unmount/unmount_unsupported.go

@@ -0,0 +1,8 @@
+//go:build windows
+// +build windows
+
+package unmount
+
+func unmount(dir string) error {
+	return nil
+}