Using an up-to-date guix (from git master), I cannot build the libsrtp
package (v1.5.4) which Qemu requires. The check phase fails:

cd test; /tmp/guix-build-libsrtp-1.5.4.drv-0/libsrtp-1.5.4/test/rtpw_test.sh >/dev/null
make: *** [Makefile:35: runtest] Error 255
phase `check' failed after 18.2 seconds

Reproducing the problem (supposing it's reproducible) should be as
simple as:

$> guix build libsrtp

When using an up-to-date guix.

Below is the complete build log.