--- a/Makefile
+++ b/Makefile
@@ -1,11 +1,11 @@
-CC=gcc
-CFLAGS=-O3 -Wall -Wextra -Wno-unknown-pragmas -Wcast-qual
-LDFLAGS=
+CC?=gcc
+CFLAGS?=-O3 -Wall -Wextra -Wno-unknown-pragmas -Wcast-qual
+LDFLAGS?=
 # CFLAGS=-O3 -Wall -Wextra -Wno-unknown-pragmas -Wcast-qual -g -fsanitize=thread
 # LDFLAGS=-g -fsanitize=thread
 # CFLAGS=-O3 -Wall -Wextra -Wno-unknown-pragmas -Wcast-qual -g -fsanitize=address
 # LDFLAGS=-g -fsanitize=address
-LIBS=-lm -lpthread -lz
+LIBS?=-lm -lpthread -lz
 ZOPFLI=zopfli/src/zopfli/
 ZOP=deflate.o blocksplitter.o tree.o lz77.o cache.o hash.o util.o squeeze.o katajainen.o symbols.o