The .exe is built outside of the current directory.. it should be in a folder like "build-Terrafirma-Desktop_Qt_5_12.." in the same directory as the main Terrafirma folder. So go into that folder, then go into release, and copy the .exe into the source folder.. of course you only need to do...
Which shader did you try it on? It should still work since XNA hasn't changed in like a decade... but also, not every .xnb is a shader, a ton of them are textures (I have other tools that will convert .xnb textures into .pngs)
edit: I suppose terraria could've updated to dx10 shaders, which...
Okay.. new Windows binaries released to support 1.3.3
OSX and Linux binaries will have to wait until monday.
Edit: bumped to version 3.0.13. (and now to 3.0.14.. stupid patches)
Edit2: OSX and Linux binaries are available now.