@kayceesrk recently finished rebasing multicore OCaml onto upstream 4.06.1 which means we get the advantage of the unified build system for Windows and Unix which was added in 4.05.0.
It’s early days, but the mingw64 port can be described as “breathing” (and in parallel)…
Keep an eye on the GitHub pull requests - I’ll push when Work in progress now at PR#173 - bytecode only (the testsuite is almost entirely passing with make world compiles completely.make -C testsuite BYTECODE_ONLY=true all-enabled) and only mingw64. The build is configured in the same way as normal (i.e. copying files, not running configure)