1. pip install cmake --default-timeout=100 -i https://pypi.tuna.tsinghua.edu.cn/simple
2. 第二个错误：
-- Building for: Visual Studio 16 2019 -- Selecting Windows SDK version to target Windows 10.0.17763. -- The C compiler identification is unknown -- The CXX compiler identification is unknown CMake Error at CMakeLists.txt:14 (project): No CMAKE_C_COMPILER could be found.
排除法首先看看VS 2017 有没有安装 Windows SDK 10.0.17763. 我是安装了SDK后好了的。
如图：
