Fix typo when trying to include curl directories

cmake/libraries/curl.cmake

@@ -8,8 +8,8 @@ find_package(CURL QUIET)
 
 if(NOT CURL_FOUND)
     set(CURL_DEFINITIONS USE_INTERNAL_CURL_HEADERS)
-    set(CURL_INCLUDE_DIR ${INTERNAL_CURL_DIR}/include)
+    set(CURL_INCLUDE_DIRS ${INTERNAL_CURL_DIR}/include)
 endif()
 
 list(APPEND CLIENT_DEFINITIONS ${CURL_DEFINITIONS})
-list(APPEND CLIENT_INCLUDE_DIRS ${CURL_INCLUDE_DIR})
+list(APPEND CLIENT_INCLUDE_DIRS ${CURL_INCLUDE_DIRS})