CMake cannot determine linker language for target

Solution 1:

You have added target for creating container library. That target contains only header files. See CMake documentation

add_library: Add a library to the project using the specified source files.

add_library( [STATIC | SHARED | MODULE] [EXCLUDE_FROM_ALL] source1 source2 ... sourceN)

Adds a library target called to be built from the source files listed in the command invocation. The corresponds to the logical target name and must be globally unique within a project. The actual file name of the library built is constructed based on conventions of the native platform (such as lib.a or .lib).

But you can not build library just from header files without any cpp file. That's why you got such error.