Make `ant war` run faster and the resulting .war file smaller

A couple months back (commit ccbcb09), before we switched to embedded Jetty (#24175 (moved)), creating the .war file ran much faster and produced a much smaller .war file than it does now: 4 seconds and 9.6M

After we switched to embedded Jetty (commit 940e00c), this changed: 71 seconds, 18M

Today, after including Relay Search (cf. #25392 (moved) and child), it takes a tiny bit longer and produces an even larger .war file: 73 seconds, 27M

Is there an easy way to improve both, performance and size?