I just realized that the post you were reading is outdated:
https://discourse.gohugo.io/t/golang-newbie-keen-to-contribute/35087/5
The build from source section of the Windows installation instructions…
…points to this Tips & Tricks topic:
https://discourse.gohugo.io/t/gcc-compiler-required-to-build-hugo-from-source-on-windows/41370
It’s mostly the same, but the compiler version is different.
You might give this a try if you have the time and inclination.
I will edit the outdated post.