  drake_install_headers(
    driving_command.h
    euler_floating_joint_state.h
    simple_car_state.h)

if(lcm_FOUND)
  drake_install_headers(
    driving_command.h
    euler_floating_joint_state.h
    simple_car_state.h)
endif()

Add lcm_FOUND guard around header vector install
Add lcm_FOUND guard around header vector install
