docs: make sphinx-build be quiet by default

The sphinx-build is fairly verbose spitting out pages of output to the
console, which causes errors from other build commands to be scrolled
off the top of the terminal. This can leave the mistaken impression that
the build passed, when in fact there was a failure.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20210812102427.4036399-1-berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
diff --git a/docs/meson.build b/docs/meson.build
index 300b134..cffe1ec 100644
--- a/docs/meson.build
+++ b/docs/meson.build
@@ -9,7 +9,7 @@
 # Check if tools are available to build documentation.
 build_docs = false
 if sphinx_build.found()
-  SPHINX_ARGS = ['env', 'CONFDIR=' + qemu_confdir, sphinx_build]
+  SPHINX_ARGS = ['env', 'CONFDIR=' + qemu_confdir, sphinx_build, '-q']
   # If we're making warnings fatal, apply this to Sphinx runs as well
   if get_option('werror')
     SPHINX_ARGS += [ '-W' ]