plugin that updates defines on buildStart hook with yarn build --watch

[s-light]

my goal is to have a simple BUILD_DATE define that updates on buildStart.
if i do something like this:

const defineBuildDatePlugin = (options) => {
    // const { destination } = options;
    function getCurrentDate() {
        return JSON.stringify(new Date().toISOString());
    }
    return {
        // inspired by https://github.com/qduld/vite-plugin-git-revision/blob/main/src/index.ts
        name: "defineBuildDatePlugin",
        config(config) {
            console.log("config(config) HOOK.");
            // console.log("config", config);
            config.define.BUILD_DATE = getCurrentDate();
        },
        buildStart(buildConfig) {
            console.log("buildStart(buildConfig)");
            // config.define.BUILD_DATE = getCurrentDate();
        },
    };
};

the config hook in yarn build --watch mode gets only triggered on the first start.
so any builds triggered by the actual watch does not get a new BUILD_DATE.

i did not find any info / how to access the config from within the buildStart Hook.
maybe i am missing something obvious ore it is just not possible this way.

i am open for any tips and hints :-)