How to overwrite variables like OPSYS, OS_VERSION?

[Hung Nguyen Gia <gh_origin%zohomail.com@localhost>]

I want to add support for MidnightBSD. This OS is weirded:

gh@gh:/usr/home/gh $ uname -s
MidnightBSD
gh@gh:/usr/home/gh $ uname -r
2.0.3
gh@gh:/usr/home/gh $ uname -a
MidnightBSD gh 2.0.3 MidnightBSD 2.0.3 #10 59f5fec7fe(stable/2.0)-dirty: Thu Dec 24 17:41:42 EST 2020     root@skunkworks:/usr/obj/usr/src/sys/GENERIC  amd64
gh@gh:/usr/home/gh $ clang -v
MidnightBSD clang version 8.0.1 (tags/RELEASE_801/final 366581) (based on LLVM 8.0.1)
Target: x86_64-unknown-freebsd11.4
Thread model: posix
InstalledDir: /usr/bin

As you see, it has it own OPSYS (MidnightBSD) and OS_VERSION (2.0.3), but it uses the FreeBSD Toolchain triplet (x86_64-unknown-freebsd11.4).

I almost success but finally fails because cwrapper confused the toolchain triplet to be x86_64-unknown-midnightbsd2.0.3

I have no idea how to fix it. Tried to overwrite it by setting it manually in bsd.prefs.mk not work.

gh