Tutorial: Update step 3 style

Help/guide/tutorial/Step3/CMakeLists.txt

@@ -14,6 +14,8 @@ option(USE_MYMATH "Use tutorial provided math implementation" ON)
 # to the source code
 configure_file(TutorialConfig.h.in TutorialConfig.h)
 
+# TODO 2: Remove EXTRA_INCLUDES list
+
 # add the MathFunctions library
 if(USE_MYMATH)
   add_subdirectory(MathFunctions)
@@ -26,6 +28,8 @@ add_executable(Tutorial tutorial.cxx)
 
 target_link_libraries(Tutorial PUBLIC ${EXTRA_LIBS})
 
+# TODO 3: Remove use of EXTRA_INCLUDES
+
 # add the binary tree to the search path for include files
 # so that we will find TutorialConfig.h
 target_include_directories(Tutorial PUBLIC

Help/guide/tutorial/Step3/MathFunctions/CMakeLists.txt

@@ -1 +1,5 @@
 add_library(MathFunctions mysqrt.cxx)
+
+# TODO 1: State that anybody linking to MathFunctions needs to include the
+# current source directory, while MathFunctions itself doesn't.
+# Hint: Use target_include_directories with the INTERFACE keyword