qemu: add support for sending QEMU stdout/stderr to virtlogd

Currently the QEMU stdout/stderr streams are written directly to
a regular file (eg /var/log/libvirt/qemu/$GUEST.log). While those
can be rotated by logrotate (using copytruncate option) this is
not very efficient. It also leaves open a window of opportunity
for a compromised/broken QEMU to DOS the host filesystem by
writing lots of text to stdout/stderr.

This makes it possible to connect the stdout/stderr file handles
to a pipe that is provided by virtlogd. The virtlogd daemon will
read from this pipe and write data to the log file, performing
file rotation whenever a pre-determined size limit is reached.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

cfg.mk

@@ -775,7 +775,7 @@ sc_prohibit_gettext_markup:
 # lower-level code must not include higher-level headers.
 cross_dirs=$(patsubst $(srcdir)/src/%.,%,$(wildcard $(srcdir)/src/*/.))
 cross_dirs_re=($(subst / ,/|,$(cross_dirs)))
-mid_dirs=access|conf|cpu|locking|network|node_device|rpc|security|storage
+mid_dirs=access|conf|cpu|locking|logging|network|node_device|rpc|security|storage
 sc_prohibit_cross_inclusion:
 	@for dir in $(cross_dirs); do					\
 	  case $$dir in							\