Add support for advzip

Allow recompressing archives before upload for
fastest possible download speeds.

cdbrelease.js

@@ -54,6 +54,21 @@ module.exports = async gitexport => {
 		});
 		zipstr.end();
 		zipstr.close();
+
+		if(config.advzip) {
+			let modeopts = [-4];
+			if(typeof config.advzip === 'number') {
+				if(config.advzip <= 4)
+					modeopts = ['-' + Math.floor(config.advzip)];
+				else
+					modeopts.push('-i', Math.floor(config.advzip));
+			}
+			const adv = spawn('advzip', ['-z', ...modeopts, zipfile], {
+				stdio: ['ignore', 'inherit', 'inherit']
+			});
+			await adv.promise;
+		}
+
 		const params = {
 			title: config.version,
 			commit: commit,