cmake: find library in argon2_LIBRARY_DIRS

CMakeLists.txt

@@ -42,8 +42,8 @@ if (NOT OPENDHT_ARGON2)
     find_package(PkgConfig)
     pkg_search_module(argon2 libargon2)
     if (argon2_FOUND)
-        message("Argon2 found " ${argon2_req})
-        set(argon2_lib ", libargon2")
+        message("-- Found Argon2: " ${argon2_LIBRARY_DIRS} " (found version \"" ${argon2_VERSION} "\")")
+        link_directories (${argon2_LIBRARY_DIRS})
     else ()
         message("Argon2 not found, using included version.")
         set(OPENDHT_ARGON2 ON)