Include Build Instructions for command line for Linux

[ClementineAccount]

Some people might not be used to CMake, either using it from command line or using it in Visual Studio's CMake. I was able to run CMake Make .. and then realized I don't know what to do and have to do troubleshooting to figure out what to do to build when there are multiple CMakeLists.txt files. I have only been familiar with either single CMakeLists.txt for command line or using Visual Studios or Visual Code's CMake extension.