+LILYPOND_BOOK_INFO_IMAGES_DIR = $(if $(INFO_IMAGES_DIR),--info-images-dir=$(INFO_IMAGES_DIR),)
+LILYPOND_BOOK_FLAGS = $(LILYPOND_BOOK_VERBOSE) $(LILYPOND_BOOK_INFO_IMAGES_DIR)
+
+ifeq ($(out),)
+LILYPOND_BOOK_PROCESS = true
+else
+LILYPOND_BOOK_PROCESS = $(LILYPOND_BINARY)
+endif
+