Ability add_subdirectory with git submodules

[vpicaver]

[vpicaver]

Since bintray has been discontinued it's hard to pull down this library by using conan. Alternatively, I would prefer to pull this repository down using a git submodule and add it to my project using add_subdirectory. I really don't want to install this library on the system since I'm planning on using it in a cross-compiling environment. It would be nice to have an option to prevent configuration generation or installation from happening.