 - drop unknown warning -Wformat-overflow=0
 - drop hardcoded -O2

Index: Makefile
--- Makefile.orig
+++ Makefile
@@ -2,7 +2,7 @@ include config.mk
 
 cflags := -Isrc/brogue -Isrc/platform -std=c99 \
 	-Wall -Wpedantic -Werror=implicit -Wno-parentheses -Wno-unused-result \
-	-Wformat -Werror=format-security -Wformat-overflow=0
+	-Wformat -Werror=format-security
 libs := -lm
 cppflags := -DDATADIR=$(DATADIR)
 
@@ -41,7 +41,7 @@ ifeq ($(DEBUG),YES)
 	cflags += -g -Og
 	cppflags += -DENABLE_PLAYBACK_SWITCH
 else
-	cflags += -O2
+	cflags +=
 endif
 
 objects := $(sources:.c=.o)
