mupdf appends their desired optimization flags to $CFLAGS this causes the optimization level configured by abuild to be overwritten. Since abuild uses -Os by default this decreases the package size. diff -upr mupdf-1.23.3.orig/Makerules mupdf-1.23.3/Makerules --- mupdf-1.23.3.orig/Makerules 2023-09-09 11:11:42.325742173 +0200 +++ mupdf-1.23.3/Makerules 2023-09-09 11:13:24.952695140 +0200 @@ -92,7 +92,7 @@ ifeq ($(build),debug) CFLAGS += -pipe -g LDFLAGS += -g else ifeq ($(build),release) - CFLAGS += -pipe -O2 -DNDEBUG + CFLAGS += -pipe -DNDEBUG LDFLAGS += $(LDREMOVEUNREACH) -Wl,-s else ifeq ($(build),small) CFLAGS += -pipe -Os -DNDEBUG