Play resources do not honor nested directories

Reported on forums at https://discuss.gradle.org/t/play-plugin-does-not-keep-directory-structure-of-resource-files/11933:

When packaging a Play application, if the resource directory conf/ has the following structure:

conf/
routes
evolutions/
default/
1.sql
2.sql
3.sql
I expect the createPlayBinaryJar task to create a jar that maintains the directory structure.

However, currently, the generated jar contains all resource files at the root, i.e.,

% jar -tf build/playBinary/lib/application.jar
META-INF/
META-INF/MANIFEST.MF
[...]
routes
1.sql
2.sql
3.sql
This causes Play database evolutions to silently fail because the evolution scripts cannot be found in evolutions/

{database name}

/.