Bringing QgisApp & Qgisappinterface to environment using osgeo4w-setup-x86_64

I am using QGIS 3 C++ API. I used osgeo4w-setup-x86_64.exe for installing QGIS. Also, I have installed qgis-dev and Qt5 within QGIS3 SDK. I need to use the QgisApp class in my application, but there is no qgisapp.h file for including in my application. But, QGIS repository have qgisapp.h in src/app.

How can I bring the QgisApp class into my environment? Should I compile the QGIS from the source code?