Update CMake file so it can be used with FetchContent in other projects

CMakeLists.txt

@@ -2,9 +2,17 @@ CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
 
 PROJECT(fast_obj)
 
-SET(CMAKE_CXX_STANDARD 11)
+OPTION(FAST_OBJ_BUILD_TEST "Build test application" OFF)
 
-ADD_EXECUTABLE(test test/test.cpp)
-TARGET_INCLUDE_DIRECTORIES(test PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
+ADD_LIBRARY(fast_obj INTERFACE)
+TARGET_INCLUDE_DIRECTORIES(fast_obj INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})
 
+ADD_LIBRARY(fast_obj_lib STATIC fast_obj.c)
+TARGET_INCLUDE_DIRECTORIES(fast_obj_lib PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 
+
+IF(${FAST_OBJ_BUILD_TEST})
+    ADD_EXECUTABLE(fast_obj_test test/test.cpp)
+    TARGET_COMPILE_FEATURES(fast_obj_test PRIVATE cxx_std_11)
+    TARGET_LINK_LIBRARIES(fast_obj_test PRIVATE fast_obj_lib)
+ENDIF()