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

	rimraf.sync(getExtensionPath(extension));

	return ext.fromMarketplace(extension.name, extension.version, extension.metadata)
		.pipe(rename(p => p.dirname = `${extension.name}/${p.dirname}`))
		.pipe(vfs.dest('.build/builtInExtensions'))
		.on('end', () => log(ansiColors.blue('[marketplace]'), extension.name, ansiColors.green('✔︎')));
}