Synology DSM helloworld package compile error written C++

Please help me. I try to compile hello world package written c++. My environment is OS : Ubuntu 14.4,and synology toolchain is bromolow 64bit compiler, But I cannot get helloworld.cgi. I don't know the reason. Source code are

#include "webman.h"

#include <string>

#include <stdio.h>

#include <synosdk/proc.h>
 
using namespace std;
 
int main(int argc, char* argv[]) {
    WebMan _cgi;
    Json::Value out;
    out["uname"] = szData;
    out["ret"] = ret;
    out["success"] = ret;
    _cgi.WriteHeader();
    _cgi.WriteBody(out);
    return 0;
}

and make file is

.PHONY: all clean
.SUFFIXES: .cgi
CXXFLAGS=$(shell pkg-config libdsm --cflags)
LDFLAGS+=$(shell pkg-config libdsm --libs)
 
# source files

SRC=${cgi_name}.cpp
CGI=$(SRC:%.cpp=../%.cgi)
 
all: $(CGI)
 
../%.cgi: %.cpp
    echo $(CXX) -o $@ $^ $(CFLAGS) $(LDFLAGS)
    $(CXX) -o $@ $^ $(CXXFLAGS) $(LDFLAGS)
 
clean:
    rm -f core *~ *.o $(CGI)

I got such error

======= Run build script =======

make: *** No rule to make target `distclean'.  Stop.
==> cgi
==> js
<== js
/usr/local/i686-linux-gnu/bin/i686-linux-gnu-ccache-g++ -o ../helloworld.cgi helloworld.cpp -I/usr/local/i686-linux-gnu/include -DSYNO_X64 -O2 -I/usr/syno/include -g -DSYNO_PLATFORM=X64 -g -DSDK_VER_MIN_REQUIRED=400 -L/usr/local/i686-linux-gnu/lib -L/usr/syno/lib -Wl,-rpath-link -Wl,/usr/syno/lib -L/usr/local/i686-linux-gnu/lib -L/usr/syno/lib -L/source/libsynocgi/lib -L/usr/syno/sqlite3/lib/ -L/source/libsynoacl/lib/ -L/source/libsynosdk/gpl/ -L/source/google-authenticator-1.x -lsynocgi -ljson -lsynowireless-core -lsynoacl -lsynogpl -lsynocoregpl -lsynobandwidth -lsynowimax -lsynosdk -lsynocore -lcrypt -lnet -licui18n -licuuc -licudata -lxml2 -lattr -lm -ldl -lz -lsqlite3 -lgoogleauth -ldsm
/usr/local/i686-linux-gnu/lib/gcc/i686-linux-gnu/4.2.1/../../../../i686-linux-gnu/bin/ld: cannot find -lnet
collect2: ld returned 1 exit status
make[2]: *** [../helloworld.cgi] Error 1
make[1]: *** [cgi] Error 2
make: *** [ui] Error 2

There is no install-dev scripts for helloworld.

Time cost: 00:00:03 [Build-->helloworld]
I got the following error:
make[2]: *** [../helloworld.cgi] Error 1
make[1]: *** [cgi] Error 2
make: *** [ui] Error 2