set up MSYS2 on windows

Apr 16, 2020

install MSYS2

Go to msys2.org and download msys2-x86_64-20190524.exe
After installed, MSYS2 is avaliable at C:\msys64\usr\bin\mintty.exe

post-install MSYS2

first, update system at the first time start up
```
pacman -Syu
```
after finish, close(NOT Ctrl+c) the window and reopen again
update again
```
pacman -Sy
pacman -Syu
```
(optional) add host environment variable C:\msys64\mingw64\bin to PATH

install toolchain in MSYS2

pacman -S mingw-w64-x86_64-toolchain make

shadow gcc

echo "alias gcc=\"x86_64-w64-mingw32-gcc\"" >> ~/.bashrc