x.js

 var bundle = browserify({
            debug: true
        })
        , code = "var process = require.modules.__browserify_process();\n" +
            "process.env.NODE_ENV = 'production'\n" +
            "require.modules.__browserify_process = function () {\n" +
            "   return process\n" +
            "}"

    var target = path.join(__dirname, "dummy.js")
    bundle.files[target] = {
        target: target
        , body: code
    }
    bundle.addEntry(path.join(__dirname, "other.js"), {
        body: "require('" + target + "')"
    })
    bundle.addEntry(input)
    var text = bundle.bundle()
    fs.writeFileSync(output, text)