Add spdlog submodule to build tree

CMakeLists.txt

@@ -41,6 +41,7 @@ dune_enable_all_packages()
 dune_require_cxx_standard(MODULE "dorie" VERSION 14)
 
 # add subdirectories
+add_subdirectory(plugins/vendor)
 add_subdirectory("m4")
 add_subdirectory("cmake/modules")
 add_subdirectory("python")

plugins/vendor/CMakeLists.txt

+# enable usage of 'add_test' in submodules (DUNE throws error otherwise)
+set(DUNE_REENABLE_ADD_TEST True)
+
+# disable spdlog tests and examples
+set(SPDLOG_BUILD_TESTING OFF)
+set(SPDLOG_BUILD_EXAMPLES OFF)
+add_subdirectory(spdlog EXCLUDE_FROM_ALL)