Remove side-effects from included cmake file

Author: xtofl

src/AddGoogleTest.cmake

@@ -3,10 +3,12 @@ cmake_minimum_required(VERSION 3.11.0)
 set(CMAKE_CXX_STANDARD 17)
 project(cpp11training)
 
-include(AddGoogleTest.cmake)
 
 project(cpp11training)
 file (GLOB_RECURSE SOURCES "${CMAKE_CURRENT_SOURCE_DIR}/*.cpp")
 add_executable(cpp11training ${SOURCES})
 include_directories(${CMAKE_CURRENT_SOURCE_DIR})
-target_link_libraries(cpp11training gtest gmock_main)
+
+include(FetchGoogleTest.cmake)
+fetch_google_test()
+target_link_libraries(cpp11training gtest)

src/CMakeLists.txt

@@ -0,0 +1,19 @@
+cmake_minimum_required(VERSION 3.11.0)
+
+include(FetchContent)
+
+function(fetch_google_test)
+	FetchContent_Declare(
+	  googletest
+	  GIT_REPOSITORY https://github.com/google/googletest.git
+	  GIT_TAG        release-1.8.0
+	)
+	FetchContent_MakeAvailable(googletest)
+	FetchContent_GetProperties(googletest)
+	if(NOT googletest_POPULATED)
+	  message(Fetching googletest)
+	  FetchContent_Populate(googletest)
+	  add_subdirectory(${googletest_SOURCE_DIR} ${googletest_BINARY_DIR})
+	endif()
+endfunction()
+