FetchContent_MakeAvailable (#3351)

* 🔧 use FetchContent_MakeAvailable

* 💚 fix test names

test/cmake_fetch_content2/CMakeLists.txt

@@ -0,0 +1,20 @@
+if (${CMAKE_VERSION} VERSION_GREATER "3.14.0")
+  add_test(NAME cmake_fetch_content2_configure
+    COMMAND ${CMAKE_COMMAND}
+    -G "${CMAKE_GENERATOR}"
+    -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
+    -Dnlohmann_json_source=${PROJECT_SOURCE_DIR}
+    ${CMAKE_CURRENT_SOURCE_DIR}/project
+  )
+  add_test(NAME cmake_fetch_content2_build
+    COMMAND ${CMAKE_COMMAND} --build .
+  )
+  set_tests_properties(cmake_fetch_content2_configure PROPERTIES
+    FIXTURES_SETUP cmake_fetch_content2
+    LABELS "git_required;not_reproducible"
+  )
+  set_tests_properties(cmake_fetch_content2_build PROPERTIES
+    FIXTURES_REQUIRED cmake_fetch_content2
+    LABELS "git_required;not_reproducible"
+  )
+endif()