WACUP is already using the newer libflac

In fact it's using code from the more recent 2018 commits (as per
https://getwacup.com/changelog/beta_0_9_9_2826.html) as that helped to fix some issues that were experienced in relation to v1.3.2 (so they could do with an official v1.3.3 sooner rather than later).
-dro