build: always use standalone asio

CMakeLists.txt

@@ -64,7 +64,6 @@ endif()
 if (OPENDHT_PROXY_SERVER OR OPENDHT_PROXY_CLIENT)
     find_package(Restinio REQUIRED)
     if (Restinio_FOUND)
-        add_definitions(-DASIO_STANDALONE)
         find_library(FMT_LIBRARY fmt)
         add_library(fmt SHARED IMPORTED)
         find_library(HTTP_PARSER_LIBRARY http_parser)
@@ -87,6 +86,9 @@ if (OPENDHT_PROXY_SERVER OR OPENDHT_PROXY_CLIENT)
         add_definitions(-DOPENDHT_PROXY_HTTP_PARSER_FORK)
     endif()
 endif()
+if (OPENDHT_PROXY_SERVER OR OPENDHT_PROXY_CLIENT OR OPENDHT_PEER_DISCOVERY)
+    add_definitions(-DASIO_STANDALONE)
+endif()
 
 # Build flags
 set (CMAKE_CXX_STANDARD 14)