It avoids propagation of lilv and patches synthpod_ui to look for other
executables in a known location.

We should probably also wrap the scripts to set PATH to where “grep”,
“coreutils”, “sed”, and “gawk” are found, but I wasn’t able to add (gnu
packages gawk) to the imports of (gnu packages music).

Unfortunately, the program crashes because it can’t find the LV2 files
for Synthpod itself:

--8<---------------cut here---------------start------------->8---
$ /gnu/store/pp3rysfcssf3kigh01mrz7jc16dgp51p-synthpod-0.1.6507/bin/synthpod_ui
error: failed to open file /home/rekado/.lv2/Synthpod_default.preset.lv2/manifest.ttl (No such file or directory)
lilv_world_load_file(): error: Error loading file `file:///home/rekado/.lv2/Synthpod_default.preset.lv2/manifest.ttl'
lilv_world_load_bundle(): error: Error reading file:///home/rekado/.lv2/Synthpod_default.preset.lv2/manifest.ttl
Plugin not found.
Synthpod 0.1.6507
Copyright (c) 2015-2016 Hanspeter Portner (dev@open-music-kontrollers.ch)
Released under Artistic License 2.0 by Open Music Kontrollers
error: failed to open file /home/rekado/dev/gx/branches/master/manifest.ttl (No such file or directory)
lilv_world_load_file(): error: Error loading file `file:///home/rekado/dev/gx/branches/master/manifest.ttl'
lilv_world_load_bundle(): error: Error reading file:///home/rekado/dev/gx/branches/master/manifest.ttl
lilv_plugins_get_by_uri failed
Segmentation fault
--8<---------------cut here---------------end--------------->8---

These probably should be looked up in $out/lib/synthpod/lv2 instead of
searching the LV2 path.

-- 
Ricardo