Error on non-debug build and add EXTRA_CFLAGS

Makefile

@@ -2,13 +2,22 @@ include config.mk
 include sources.mk
 
 ifeq (${CC},clang)
+
 CFLAGS =\
 	-std=c99\
 	-Weverything\
 	-Wno-padded\
 	-Wno-disabled-macro-expansion\
 	-pedantic
+
+ifeq (${DEBUG},1)
+CFLAGS += -g
+else
+CFLAGS += -O2 -Werror
+endif
+
 else ifeq (${CC},gcc)
+
 CFLAGS =\
 	-std=c99\
 	-Wall\
@@ -27,14 +36,16 @@ CFLAGS =\
 	-Wunsafe-loop-optimizations\
 	-Wparentheses\
 	-pedantic
-endif
 
 ifeq (${DEBUG},1)
 CFLAGS += -g
 else
-CFLAGS += -O2
+CFLAGS += -O2 -Werror
 endif
 
+endif
+CFLAGS += ${EXTRA_CFLAGS}
+
 OBJ = ${SRC:.c=.o}
 
 all: ${OBJ}