There is command in UAT (unreal’s replacement of make) to build plugin, you might deduce something from here
Alternaticly you can do it more hackish way, you can move plugin to game project (disable original plugin first) and compile it there, and then move back to engine forder
I don’t use lacuher version anymore for long time, but check if there is GenerateProjectFiles.bat or Setup.bat somewhere in main engine directories, they should generate project files for engine from it source files