Bumping citra to latest version, running into unexplained behavior

I’m rather new to NixOS and even newer to NixOS package development. I wanted a certain feature that a newer version of Citra, the 3DS emulator, offers, so I thought I would try and contribute a little bit by sending in a PR. The problem is simply bumping the version doesn’t work. I’ve been working with the nightly version to solve this problem, and here is the error I get:

As you can see, a certain file doesn’t exist. This file, constant_propagation_pass.cpp, exists in ir/opt, not in ir/var/empty. As I’ve said, I’m new to NixOS development, but to me it seems as if /opt is being replaced with /var/empty.

For more information, I found that this error began showing up at nightly-1802 right after nightly-1801. I’m tearing my hair out at this point because I have nowhere left to go but the forums. Can anyone help me out?

For those curious about the progress of this, I have a solution here. Its not perfect, but if you really the latest version of Citra, go ahead and build it from my PR or my fork.