docs: update readme with libgflags (#21293)

README-CN.md

@@ -52,7 +52,7 @@ TDengine 还提供一组辅助工具软件 taosTools，目前它包含 taosBench
 ### Ubuntu 18.04 及以上版本 & Debian：
 
 ```bash
-sudo apt-get install -y gcc cmake build-essential git libssl-dev
+sudo apt-get install -y gcc cmake build-essential git libssl-dev libgflags2.2 libgflags-dev
 ```
 
 #### 为 taos-tools 安装编译需要的软件

README.md

@@ -60,7 +60,7 @@ To build TDengine, use [CMake](https://cmake.org/) 3.0.2 or higher versions in t
 ### Ubuntu 18.04 and above or Debian
 
 ```bash
-sudo apt-get install -y gcc cmake build-essential git libssl-dev
+sudo apt-get install -y gcc cmake build-essential git libssl-dev libgflags2.2 libgflags-dev
 ```
 
 #### Install build dependencies for taosTools