Allow setting build env variables such as GOOS=windows GOARCH=amd64

[the0rem]

We have a windows-specific app that needs to be built from both our local machines (MacOS) as well as our CI (Linux). We can set environment variable in CI however local development is hindered with this limitation and doesn't really fall within the NX approach if you have to set variables outside of the build tooling.

One suggestion is to pass the cwd option to the runGoCommand when building. This would allow you to set any environmental variables required.

I'm not sure how you cater for this in https://github.com/nx-go/nx-go/blob/main/packages/nx-go/src/executors/build/executor.ts as the file naming logic is looking at the platform to decide whether to set the file extension.