MSYS will drop Windows 7; find an alternative to it for MinGW-w64

[andlabs]

https://www.msys2.org/docs/windows_support/

I have no intention to ever drop Windows 7 support. MinGW of some sort is required to static link with Go, which is a requirement for me personally.

[msink]

msys2/MINGW-packages#10088
msys2/MSYS2-packages#2696

[lazka]

I'm sure the toolchains will be able to build for win7 for a bit longer then that. If there are any issues let us know.