[build] cross building on linux is not working

circle CI job is failing with the following error, can be reproduced locally on a linux machine (make release)

Unsupported `GLOBAL_AGENT.HTTP_PROXY` configuration value: URL protocol must be "http:".

Full logs from Circle CI:

npm run release:cross

> crc-tray@1.2.0 release:cross
> npm run build && npm run build:react && electron-packager . --ignore='/frontend/package.json' --ignore='/frontend/node_modules' --ignore='/frontend/src' --overwrite --asar --out=release --platform=darwin,win32 --prune=true --icon=assets/appicon --app-bundle-id='com.redhat.codeready.containers'

> crc-tray@1.2.0 build
> tsc -p .

> crc-tray@1.2.0 build:react
> cd frontend && npm run build

> frontend@0.1.0 build
> react-scripts build

Creating an optimized production build...
Compiled successfully.

File sizes after gzip:

  90.62 kB  build/static/js/main.b7e1ce78.js
  37.17 kB  build/static/css/main.f962c967.css

The project was built assuming it is hosted at ./.
You can control this with the homepage field in your package.json.

The build folder is ready to be deployed.

Find out more about deployment here:

  https://cra.link/deployment

Unsupported `GLOBAL_AGENT.HTTP_PROXY` configuration value: URL protocol must be "http:".

Exited with code exit status 1

CircleCI received exit code 1

crc-org / tray-electron

[build] cross building on linux is not working #203