LILYPOND_BOOK_INFO_IMAGES_DIR = $(if $(INFO_IMAGES_DIR),--info-images-dir=$(INFO_IMAGES_DIR),)
LILYPOND_BOOK_FLAGS = $(LILYPOND_BOOK_VERBOSE) $(LILYPOND_BOOK_INFO_IMAGES_DIR)
LILYPOND_BOOK_INFO_IMAGES_DIR = $(if $(INFO_IMAGES_DIR),--info-images-dir=$(INFO_IMAGES_DIR),)
LILYPOND_BOOK_FLAGS = $(LILYPOND_BOOK_VERBOSE) $(LILYPOND_BOOK_INFO_IMAGES_DIR)