How to compile C++ library inside ROS package?

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I have a package structured as follows:

-include
-src
-my_submodule
  -include
  -src
  CMakeLists.txt
CMakeLists.txt
package.xml

The my_submodule folder is basically a C++ library that I want to compile along with my ROS package and use as a dependency. I could install my_submodule and use find_package(my_submodule), but I want to compile my_submodule along with the package.

What do I need to modify to compile my_submodule along with my package? The idea is that my_submodule is not dependent on ROS or my package, but I want to include without installing separately.