tests: disable part of msg_name test on non-glibc systems
tests: disable part of msg_name test on non-glibc systems

Sadly, musl recvmsg wrapper blindly dereferences 2nd argument,
so limit the affected part of the test to glibc that doesn't.

* tests/msg_name.c (test_msg_name) [!__GLIBC__]: Do not test
with inaccessible 2nd argument.

cuviper/strace,Saruta/strace,cuviper/strace,Saruta/strace,Saruta/strace,Saruta/strace,Saruta/strace,cuviper/strace,cuviper/strace,cuviper/strace