Since commit 3871f8be8d
("pulseaudioFull: fix wrapGApp wrapping"), the pulseaudio service files
have been referencing *unwrapped* binaries. This mostly hurts
pulseaudioFull, where using unwrapped binaries means there's no High
Fidelity A2DP profile at all. Plain pulseaudio (not -full) seems able to
use A2DP profile with SBC codec, but not aptX, as the latter requires
gstreamer / wrapper.
Since the wrapping of pulseaudio is a bit complicated (see referenced
commit), let's just fix the service files manually in preFixup.
Ref https://github.com/NixOS/nixpkgs/issues/203919.
c26ff1ed9b