build: Fix CMake and ns3 script bugs, add a test suite and fix formatting

examples/CMakeLists.txt

@@ -1,10 +1,12 @@
-if(${NS3_EXAMPLES})
+if(${EXAMPLES_ENABLED})
   subdirlist(examples_to_build ${CMAKE_CURRENT_SOURCE_DIR})
 
   # Process subdirectories
   foreach(examplefolder ${examples_to_build})
     add_subdirectory(${examplefolder})
 
-    set(ns3-example-folders "${examplefolder};${ns3-example-folders}" CACHE INTERNAL "list of example folders")
+    set(ns3-example-folders "${examplefolder};${ns3-example-folders}"
+        CACHE INTERNAL "list of example folders"
+    )
   endforeach()
 endif()