build/lib/builtInExtensions.ts/syncMarketplaceExtension
function syncMarketplaceExtension(extension: IExtensionDefinition): Stream {
	const galleryServiceUrl = productjson.extensionsGallery?.serviceUrl;
	const source = ansiColors.blue(galleryServiceUrl ? '[marketplace]' : '[github]');
	if (isUpToDate(extension)) {
		log(source, `${extension.name}@${extension.version}`, ansiColors.green('✔︎'));
		return es.readArray([]);
	}

	rimraf.sync(getExtensionPath(extension));

	return getExtensionDownloadStream(extension)
		.pipe(vfs.dest('.build/builtInExtensions'))
		.on('end', () => log(source, extension.name, ansiColors.green('✔︎')));
}