Exclude external project sub directory

I'm creating a project using Cmake and I'm using ExternalProject to include a dependency. That dependency has its own CMakeLists.txt and inside of that CMakeLists.txt it includes two more directories using add_subdirectory and those directories are examples and I want to remove them.

For example:

ExternalProject_Add(
  foobar
  URL url_goes_here
  PREFIX ${CMAKE_CURRENT_BINARY_DIR}/vendor/foobar
  INSTALL_COMMAND ""
)

Inside of the CMakeLists.txt of foobar it has add_subdirectory(example1) and add_subdirectory(example1).

I want to remove those two examples from being built.