Build system: warn about missing references when building the manual

meson.build

@@ -611,7 +611,7 @@ endif
 
 dynare_manual_html = custom_target('dynare-manual.html',
                                    output : 'dynare-manual.html', input : sphinx_src,
-                                   command : [ sphinx_build_exe, '-b', 'html', sphinx_defines,
+                                   command : [ sphinx_build_exe, '-n', '-b', 'html', sphinx_defines,
                                                '-d', '@PRIVATE_DIR@',
                                                meson.current_source_dir() / 'doc/manual/source',
                                                '@OUTPUT@' ],

scripts/sphinx-build-pdf-wrapper

@@ -18,7 +18,7 @@ shift 4
 # -D options are passed, presumably due to a bug in sphinx-build.
 # See: https://bugs.debian.org/933347
 
-"$sphinx_build_exe" -b latex "$@" "$source_dir" "$private_dir"
+"$sphinx_build_exe" -n -b latex "$@" "$source_dir" "$private_dir"
 
 make -C "$private_dir" all-pdf