Since about a week or two ago, the alsa-utils tools such as amixer and
alsamixer fail to start:

--8<---------------cut here---------------start------------->8---
> amixer
ALSA lib dlmisc.c:292:(snd1_dlobj_cache_get) Cannot open shared library /gnu/store/5cbff8yc8f8qgcjrikmdf32pg4jy7inp-alsa-lib-1.1.6/lib/alsa-lib/libasound_module_ctl_pulse.so ((null): /gnu/store/5cbff8yc8f8qgcjrikmdf32pg4jy7inp-alsa-lib-1.1.6/lib/alsa-lib/libasound_module_ctl_pulse.so: cannot open shared object file: No such file or directory)
amixer: Mixer attach default error: No such device or address
--8<---------------cut here---------------end--------------->8---

And the aforementioned file is missing indeed.

I see that in commit 2101cc3fb691f443b830fdf5f846ded5fa018739 Julien
patched alsa-lib to use ALSA_PLUGIN_DIR.  Could be the culprit?

-- 
Pierre Neidhardt

Luck, that's when preparation and opportunity meet.
		-- P.E. Trudeau