It's a goal of mine to get Valve using Nix. (I hope our in-progress Windows support would make this especially compelling.)
One advantage of this is that it will become very easy to not only build the original source of the game, but also build it with the original toolchain and dependencies, the toolchains for those dependencies, etc. etc., all the way down.
Hopefully something like that at your finger trips would have made finding the root cause of this bug a good bit easier!
On Nixpkgs master, you can cross compile to MinGW and Cygwin.
Native Cygwin builds are also currently in progress: https://github.com/NixOS/nixpkgs/pull/447520. I would expect this to be done very soon, there year even (holidays permitting).
There is a MinGW build of Nix but it is missing some features. There has been MSVC build of a fork in the past and I would like to revive that also.
There some some open questions relating to Nixpkgs's heavy use of Bash, but longer term I would like to compete for Windows in all ways:
Maybe I'm not seeing it. How would the bug finding be easier here? Seems like the same setup. They could compile with recent tools, and they already had the compiled version with old tools (hosted on Steam).
One advantage of this is that it will become very easy to not only build the original source of the game, but also build it with the original toolchain and dependencies, the toolchains for those dependencies, etc. etc., all the way down.
Hopefully something like that at your finger trips would have made finding the root cause of this bug a good bit easier!