War plugin not including src/main/webapp

Does anyone know if it is possible to configure the standard war task such that excludes all default files and only uses directories that I directly specify ?

I have the ‘original’ source code (html, js files etc) under src/main/webapp but run everything through optimizers via require.js such that the new root is under ‘build/main’

If I just specify it like this I also have the original files from src/main/webapp included

war {
       from 'build/main'

Is there a way to exclude the default webapp root ?

The workaround so far is to specify a non-existent webAppDir like this webAppDirName = ‘notused