Please support Windows

[Nuru]

I would like to be able to run commands on Windows, which go generally supports, but Variant has some deep dependency that uses system calls (via the outdated syscall) not supported on Windows.

$ go version
go version go1.15.11 linux/amd64
$ variant export go cli build
go: creating new go.mod: module example.com/cli
go: github.com/rakyll/statik upgrade => v0.1.7
$ cd build
$ GOOS=windows GOARCH=amd64 go build
# github.com/k-kinzal/aliases/pkg/aliases/script
/conf/go/pkg/mod/github.com/k-kinzal/[email protected]/pkg/aliases/script/script.go:100:42: unknown field 'Setpgid' in struct literal of type syscall.SysProcAttr
/conf/go/pkg/mod/github.com/k-kinzal/[email protected]/pkg/aliases/script/script.go:150:9: undefined: syscall.Kill