added config level option to enable tests

CMakeLists.txt

 cmake_minimum_required(VERSION 3.16)
 
-if(NOT DEFINED PROJECT_NAME) # detection for disabling test inspired by Catch2
-  set(NOT_SUBPROJECT ON)
-else()
-  set(NOT_SUBPROJECT OFF)
-endif()
+option(EMLABCPP_TESTS_ENABLED "Decides whenever tests should be enabled" OFF)
 
 project(emlabcpp)
 
 add_library(emlabcpp INTERFACE)
 target_include_directories(emlabcpp INTERFACE include/)
 
-if(NOT_SUBPROJECT)
+if(EMLABCPP_TESTS_ENABLED)
     include(CTest)
     if(BUILD_TESTING)
         add_subdirectory(tests)

Makefile

@@ -8,7 +8,7 @@ clean:
 	rm -rf ./build
 
 build_test:
-	cmake -Bbuild $(EXTRAARGS) -DCMAKE_EXPORT_COMPILE_COMMANDS=1
+	cmake -Bbuild $(EXTRAARGS) -DEMLABCPP_TESTS_ENABLED=ON -DCMAKE_EXPORT_COMPILE_COMMANDS=1
 	make -Cbuild -j
 
 exec_test: build_test