add dummy benchmark project

CMakeLists.txt

@@ -10,9 +10,14 @@ project(flat.hpp)
 add_library(${PROJECT_NAME} INTERFACE)
 target_include_directories(${PROJECT_NAME} INTERFACE headers)
 target_compile_features(${PROJECT_NAME} INTERFACE cxx_std_14)
-add_library(${PROJECT_NAME}::${PROJECT_NAME} ALIAS ${PROJECT_NAME})
 
 if(BUILD_AS_STANDALONE)
+    option(BUILD_WITH_UNBENCH "Build with benchmarks" OFF)
+    if(BUILD_WITH_UNBENCH)
+        enable_testing()
+        add_subdirectory(unbench)
+    endif()
+
     option(BUILD_WITH_UNTESTS "Build with unit tests" ON)
     if(BUILD_WITH_UNTESTS)
         enable_testing()