specify which architecture to target by setting WIN_ARCH env var
This allows bundling much newer zbar that includes many fixes. related: #6018 This is largely based on https://github.com/Electron-Cash/Electron-Cash/pull/1362 https://github.com/Electron-Cash/Electron-Cash/pull/1363 https://github.com/Electron-Cash/Electron-Cash/pull/1365 eda015908e
eda015908e