Otherwise "make distcheck" will have to regenerate it, which means
that it will have to regenerate doc/pspp.xml (because it depends on
help-pages-list) but that's not possible under "make distcheck"
because it makes the source directory read-only.
Found by PSPP autobuilder.
src/ui/gui/var-type-dialog.ui
-doc/help-pages-list: $(UI_FILES)
+$(srcdir)/doc/help-pages-list: $(UI_FILES)
cat $^ | grep '"help-page"' | \
sed -e 's% *<property name="help-page">\([^<]*\)</property>%//*[@id='"'"'\1'"'"']%' \
-e 's%#%'"'"']/*[@id='"'"'%g' > $@
+EXTRA_DIST += doc/help-pages-list
EXTRA_DIST += \