util: Add qemu_guest_getrandom and associated routines

This routine is intended to produce high-quality random numbers to the
guest.  Normally, such numbers are crypto quality from the host, but a
command-line option can force the use of a fully deterministic sequence
for use while debugging.

Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/util/Makefile.objs b/util/Makefile.objs
index 9206878..c27a923 100644
--- a/util/Makefile.objs
+++ b/util/Makefile.objs
@@ -54,5 +54,6 @@
 util-obj-$(CONFIG_INOTIFY1) += filemonitor-inotify.o
 util-obj-$(CONFIG_LINUX) += vfio-helpers.o
 util-obj-$(CONFIG_OPENGL) += drm.o
+util-obj-y += guest-random.o
 
 stub-obj-y += filemonitor-stub.o