qemu-ga: check if utmpx.h is available on the system

Commit 161a56a9065 added command guest-get-users and requires the
utmpx.h (defined by POSIX) to work. It is however not always available
(e.g. on OpenBSD) therefor a check for its existence is necessary.

Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>
Message-id: 8c99564250c916aa0bd3484071bbb0f1ad4d8cf3.1500299896.git.tgolembi@redhat.com
2 files changed