gpg：：MD5(char const*， int)： 错误： 未定义对'MD5_Init'的引用

当我使用NDK R10（最新版本）编译google play服务示例极简主义时，我遇到了这些错误，我尝试使用LOCAL_STATIC_LIBRARIES，但错误仍然相同。

Android NDK: WARNING:jni/Android.mk:native-activity: non-system libraries in lin
ker flags: -lgnustl_static
Android NDK:     This is likely to result in incorrect builds. Try using LOCAL_S
TATIC_LIBRARIES
Android NDK:     or LOCAL_SHARED_LIBRARIES instead to list the library dependenc
ies of the
Android NDK:     current module
[armeabi] Compile++ thumb: native-activity <= main.cpp
[armeabi] Compile++ thumb: native-activity <= StateManager.cpp
[armeabi] Compile thumb  : android_native_app_glue <= android_native_app_glue.c
[armeabi] StaticLibrary  : libandroid_native_app_glue.a
[armeabi] SharedLibrary  : libnative-activity.so
jni/../../gpg-cpp-sdk/android/lib/gnustl/armeabi/libgpg.a:turn_based_match_impl.
pb.cc:function gpg::MD5(char const*, int): error: undefined reference to 'MD5_In
it'
jni/../../gpg-cpp-sdk/android/lib/gnustl/armeabi/libgpg.a:turn_based_match_impl.
pb.cc:function gpg::MD5(char const*, int): error: undefined reference to 'MD5_Up
date'
jni/../../gpg-cpp-sdk/android/lib/gnustl/armeabi/libgpg.a:turn_based_match_impl.
pb.cc:function gpg::MD5(char const*, int): error: undefined reference to 'MD5_Fi
nal'
jni/../../gpg-cpp-sdk/android/lib/gnustl/armeabi/libgpg.a:turn_based_match_impl.
pb.cc:function gpg::ContentMD5AtPath(std::string const&, std::string const&): er
ror: undefined reference to 'MD5_Init'
jni/../../gpg-cpp-sdk/android/lib/gnustl/armeabi/libgpg.a:turn_based_match_impl.
pb.cc:function gpg::ContentMD5AtPath(std::string const&, std::string const&): er
ror: undefined reference to 'MD5_Update'
jni/../../gpg-cpp-sdk/android/lib/gnustl/armeabi/libgpg.a:turn_based_match_impl.
pb.cc:function gpg::ContentMD5AtPath(std::string const&, std::string const&): er
ror: undefined reference to 'MD5_Final'

谢谢。