Ubuntu编译生成libevent库

1. 下载libevent

2. 配置
   2.1 ./configure --prefix=/usr/lib/libevent
   报错如下

   configure: error: openssl is a must but can not be found. You should add the directory containing `openssl.pc' to the `PKG_CONFIG_PATH' environment variable, or set `CFLAGS' and `LDFLAGS' directly for openssl, or use `--disable-openssl' to disable support for openssl encryption

   2.2 解决方法：
   需要配置环境变量PKG_CONFIG_PATH为openssl.pc的路径，Ubuntu已经装了openssl，但是找不到openssl.pc，原因是没有安装 libssl-dev。
   输入命令： sudo apt install -y libssl-dev 后安装后可以找到openssl.pc的路径：/usr/lib/x86_64-linux-gnu/pkgconfig/openssl.pc

   2.3 配置环境变量PKG_CONFIG_PATH后，2.1的命令可以执行成功

3. 编译
   1) make
   2) sudo make install
4. 查看结果
   ll /usr/lib/libevent