Use a closure to setup proguard's config files.

This allows to compute the list only when the
task is about the run and to properly handle cases where
only the config files are touched (and trigger a new task
execution).

Change-Id: I55aa4d7bdfc4ef95532757a009921de653f20ced
(cherry picked from commit 89b3a4234b00f4f57011c1a3e6450607f26a57b2)
2 files changed