Makefile: disable Sphinx nitpicking

Turn off Sphinx nitpicking as a temporary (?) measure so
sphinx builds complete even with warnings about missing
references.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20190521122519.12573-11-peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Makefile

@@ -1001,7 +1001,7 @@ sphinxdocs: $(MANUAL_BUILDDIR)/devel/index.html $(MANUAL_BUILDDIR)/interop/index
 # Note the use of different doctree for each (manual, builder) tuple;
 # this works around Sphinx not handling parallel invocation on
 # a single doctree: https://github.com/sphinx-doc/sphinx/issues/2946
-build-manual = $(call quiet-command,CONFDIR="$(qemu_confdir)" sphinx-build $(if $(V),,-q) -W -n -b $2 -D version=$(VERSION) -D release="$(FULL_VERSION)" -d .doctrees/$1-$2 $(SRC_PATH)/docs/$1 $(MANUAL_BUILDDIR)/$1 ,"SPHINX","$(MANUAL_BUILDDIR)/$1")
+build-manual = $(call quiet-command,CONFDIR="$(qemu_confdir)" sphinx-build $(if $(V),,-q) -W -b $2 -D version=$(VERSION) -D release="$(FULL_VERSION)" -d .doctrees/$1-$2 $(SRC_PATH)/docs/$1 $(MANUAL_BUILDDIR)/$1 ,"SPHINX","$(MANUAL_BUILDDIR)/$1")
 # We assume all RST files in the manual's directory are used in it
 manual-deps = $(wildcard $(SRC_PATH)/docs/$1/*.rst) $(SRC_PATH)/docs/$1/conf.py $(SRC_PATH)/docs/conf.py