将项目与静态构建卷曲链接

我正在使用CMake和MinGW32在C++中做小项目,这需要libcurl库,但是当我尝试静态链接构建libcurl.a时,我得到了未定义的引用错误

undefined reference to `_imp__curl_easy_init'
undefined reference to `_imp__curl_easy_setopt'
undefined reference to `_imp__curl_easy_perform'
undefined reference to `_imp__curl_easy_getinfo'
undefined reference to `_imp__curl_easy_strerror'

我在dep/curl中有cURL源代码,在src文件夹中有源代码.这就是我的项目的CMakeLists.txt的样子:

project(ShutdownServer)
cmake_minimum_required(VERSION 2.8)
set(CMAKE_BUILD_TYPE "Release")
set(CURL_STATICLIB true)
set(BUILD_CURL_EXE false)

add_subdirectory(dep/curl)
set(TARGET_NAME "ShutdownServer")
set(LIBCURL_DIR ${PROJECT_SOURCE_DIR}/dep/curl)

aux_source_directory(src SRC_LIST)
add_executable(${TARGET_NAME} ${SRC_LIST})

find_path(LIBCURL_INCLUDE_DIR curl/curl.h HINTS ${LIBCURL_DIR}/include)
include_directories(${LIBCURL_INCLUDE_DIR})

add_dependencies(${TARGET_NAME} libcurl)

set(LIBS ${LIBS} ws2_32)
set(LIBS ${LIBS} iphlpapi)
set(LIBS ${LIBS} libcurl)

target_link_libraries(${TARGET_NAME} ${LIBS})

set(CMAKE_EXE_LINKER_FLAGS "-static -static-libgcc -static-libstdc++")

当我将CURL_STATICLIB选项切换为false并动态生成libcurl时,项目构建正常,但我宁愿将所有内容构建到一个二进制文件中.有人可以告诉我这有什么问题吗？