Clion
CLion is a commercial Cross-Platform IDE for C and C++ by JetBrains.
JetBrains supports non-commercial open-source projects by providing licenses to contributors free of charge. You can apply here.
For CLion 2019.3.5.
Open CLion.
Select Open 
Open the preferences window and navigate to Build, Execution, Deployment > CMake
This is the Mixxx Wiki - 
Mixxx is a free and open-source DJ software.
Manual
Hardware Compatibility
Reporting Bugs
Getting Involved
Contribution Guidelines
Coding Guidelines
Using Git
Developer Guide
Creating Skins
Contributing Mappings
Mixxx Controls
MIDI Scripting
Components JS
HID Scripting