Based on the 64bit time related errors, my first guess is that you are
- using a newer musl 1.2.2 (or later) with 64bit time symbols in your Windows buildhost (and thus in your compiled program), but
- using OpenWrt 21.02.x with the older musl 1.1.24 version with 32bit time handling.
If that is the reason, try 22.03.0-rc1 or master.