Does not build in MSYS shell

[nikserg]

Trying to build using MSYS shell, but get error, which clearly says, that I'm using MSYS, but it expects MSYS, lol.

$ go run build.go -verbose build-all
2022/01/17 11:56:59 This has to be run in a MSYS or MinGW64 shell, uname output: MSYS_NT-10.0-19042 PK011 3.3.3-341.x86_64 2022-01-16 14:36 UTC x86_64 Msys
exit status 1

[cretz]

tor-static/build.go

Line 83 in f09ce66

} else if !bytes.HasPrefix(byts, []byte("MINGW64")) && !bytes.HasPrefix(byts, []byte("MSYS2")) {

is expecting MINGW64 or MSYS2. Seems others have included "MSYS_NT", e.g. https://github.com/conan-io/conan/pull/2798/files. I am ok with a PR that does the same here if you're willing to submit it. Otherwise, I haven't really updated this project in years and am unsure when I'll revisit it.