Cross-Build Mac and Windows binaries from linux

[dragetd]

Is your feature request related to a problem? Please describe.
Requiring CI runner with Windows and Mac can be a huge PITA.

Describe the solution you'd like
Enable building windows/mac binaries under Linux.

Related to #162

[dragetd]

There is a nice blog entry about someone building a docker image to build go with cgo for Windows under Linux
https://dh1tw.de/2019/12/cross-compiling-golang-cgo-projects/

[MMulthaupt]

Major reason for why Windows is a problem is the need to make RDP logins to enable signing capability.

• https://gist.github.com/trollixx/6abc5c3769c621ecc485

[dragetd]

Possible signing fix https://stackoverflow.com/questions/18287960/signing-windows-application-on-linux-based-distros ?