support msys2 on windows

[realysy]

With msys2, people can install package like gcc/g++, cmake, curl, openssl, sqlite and nlohmann using pacman. It is another popular way to develop C++ program on windows besides compiling with MSVC cl compiler.

There are multiple environments provided by msys2, such as ucrt64 and mingw64, and the ucrt64 env is the recommanded environment, so if one environment has to be choosen to support, ucrt64 should be a good choice.