bug#15615: Pulseaudio build fails

[David Thompson]

`guix build pulseaudio` fails because of the following test:
Running suite(s): Memblock
shm_open() failed: Function not implemented
0%: Checks: 1, Failures: 1, Errors: 0
tests/memblock-test.c:86:F:memblock:memblock_test:0: Assertion 'pool_a 
!= NULL' failed
FAIL: memblock-test

Does this happen for anyone else or just me?

- Dave