Re-enabled tracing for external project builds

[jellehierck]

In 01c9f0e, the tracing functionality was wrapped with an "project name guard" (if that is a real name) preventing it from running when embedded in another project:

if(${CMAKE_PROJECT_NAME} STREQUAL ${PROJECT_NAME})
  if (ENABLE_TRACING)
    ...
  endif()
endif()

However, this caused tracing to be disabled for any projects which include cactus_rt in CMake with FetchContent as suggested in the README. This is IMO one of the best features of cactus_rt and I would love to have it back.

This pull request reverts the "project name guard" around the tracing sources and protobuf folder include. I also included a status message indicating that tracing will also be built.

I assume this functionality was added because of ROS 2 support (very excited about that BTW!) since the tracing might interfere? If so, perhaps another option is to enable/disable the tracing based on the ENABLE_ROS2 flag instead of the project name guard, making it configurable.

[jellehierck]

As an addition which might be included in the README:

You can set/unset the enable options in CMake with the following code by calling set() BEFORE FetchContent_MakeAvailable():

include(FetchContent)
FetchContent_Declare(
    cactus_rt
    GIT_REPOSITORY [email protected]:jellehierck/cactus-rt.git
    GIT_TAG d0a0854feaef7750c24a703db7e29dc71f019123 # latest commit as of 02-10-2024
)
set(ENABLE_TRACING OFF)  # <-- Disable tracing BEFORE FetchContent_MakeAvailable
FetchContent_MakeAvailable(cactus_rt)

This was inspired by this stackoverflow question