Get rid of "out/.info-images-dir.dep" warning, and
remove debugging output
$(outdir)/%.texi: $(outdir)/%.tely
- echo $(LILYPOND_BOOK_PROCESS)
$(PYTHON) $(LILYPOND_BOOK) $(LILYPOND_BOOK_INCLUDES) --process='$(LILYPOND_BOOK_PROCESS) $(LILYPOND_BOOK_INCLUDES) $(LILYPOND_BOOK_LILYPOND_FLAGS)' --output=$(outdir) --format=$(LILYPOND_BOOK_FORMAT) $(LILYPOND_BOOK_FLAGS) $<
#
# DON'T REMOVE SOURCE FILES, otherwise the .TEXI ALWAYS OUT OF DATE.
# symlinks, see replace_symlinks_urls in
# buildscripts/add_html_footer.py.
-ifneq ($(INFO_IMAGES_DIR),)
+ifneq ($(INFO_IMAGES_DIR),'')
# make dereferences symlinks, and $(INFO_IMAGES_DIR) is a symlink
# to $(outdir), so we can't use directly $(INFO_IMAGES_DIR) as a