pulseaudio: needs dynamic library support

Fixes:
http://autobuild.buildroot.net/results/75a/75a3380fdcce88f1f9f2a77c4f059787623919d7/
http://autobuild.buildroot.net/results/f4a/f4a22344bd5c8f59e6f8cacb6a549f8d8fe99af2/



Pulseaudio uses dlfcn.h, so it cannot work in a pure static environment.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>