Add missing dep patterns for .pieo

While adding sanitizer support, I noticed that all other extensions were
handled but .pieo was missing.

Reviewed By: emaste, imp
MFC after: 1 week

Differential Revision: https://reviews.freebsd.org/D31040

(cherry picked from commit 2d78130185b5518e0bdb4a2f3c5d5ede6773312d)