用cmake构建DPDK l2fwd

1. 下载DPDK源码，进入examples/l2fwd 目录

2. 设置好PKG_CONFIG_PATH和LD_LIBRARY_PATH，分别用于编译和运行

export PKG_CONFIG_PATH=/opt/dpdk/dpdk-22.07/bin/lib/aarch64-linux-gnu/pkgconfig/
export LD_LIBRARY_PATH=/opt/dpdk/dpdk-22.07/bin/lib/aarch64-linux-gnu/

3. 创建CMakeLists.txt, 并写入如下内容：

project (l2fwd)
find_package(PkgConfig)
pkg_search_module