what this
How did you run the project? I searched the error message and it seems related to a Linker error in VS Code. For example, this link discusses changing the Linker settings to solve the error[1]. CMIIW.
You can probably open an issue if the error persists and you can't run the app, although it seems unlikely as long as you follow the guide. I assume you use Windows, have you made sure to do what the developer suggests before running it on VS Code?
Install CUDA SDK and open BTCCollider.sln in Visual C++ 2017.
You may need to reset your Windows SDK version in project properties.
In Build->Configuration Manager, select the Release configuration.
Build and enjoy.
Note: The current release has been compiled with CUDA SDK 10.0, if you have a different release of the CUDA SDK, you may need to update CUDA SDK paths in BTCCollider.vcxproj using a text editor. The current nvcc option are set up to architecture starting at 3.0 capability, for older hardware, add the desired compute capabilities to the list in GPUEngine.cu properties, CUDA C/C++, Device, Code Generation.
Source:
https://github.com/JeanLucPons/BTCCollider[1]
https://stackoverflow.com/questions/33400777/error-lnk2019-unresolved-external-symbol-main-referenced-in-function-int-cde