Compile static library explicitly

Author: an-tao

CMakeLists.txt

@@ -79,7 +79,7 @@ if(CARES_INCLUDE_DIR AND CARES_LIBRARY)
 else()
     set(TRANTOR_SOURCES ${TRANTOR_SOURCES} trantor/net/inner/NormalResolver.cc)
 endif()
-add_library(trantor ${TRANTOR_SOURCES})
+add_library(trantor STATIC ${TRANTOR_SOURCES})
 set_property(TARGET trantor PROPERTY CXX_STANDARD 14)
 set_property(TARGET trantor PROPERTY CXX_STANDARD_REQUIRED ON)
 set_property(TARGET trantor PROPERTY CXX_EXTENSIONS OFF)