games/retroarch: Fix build if multimedia/pipewire installed
This does not affect clean builds (as with Poudriere).
PR: 289429
Approved by: Daniel Menelkir <dmenelkir@gmail.com> (maintainer, implicit - fix build)
MFH: 2025Q3
(cherry picked from commit 8f270dd4b52979124c89a3bacb137c69d93d2255)