preserveWatchOutput: true doesn't work anymore in 3.0.0-rc

[Tyriar]

Just testing the RC on https://github.com/xtermjs/xterm.js, it has a watch task (yarn watch) which uses concurrently to fire off several tsc tasks, all of which use "preserveWatchOutput": true. With the RC the setting is being ignored and the terminal clearing is happening again.

This is what I see in my terminal after doing the build, notice it's only showing the last start watch at the top of the buffer:

[Tyriar]

Thanks @sheetalkamat!