Add optional -DDEBUG to Makefile.

build/Makefile

@@ -1,4 +1,5 @@
 PRG := st-util
+DEBUG := #-DDEBUG
 
 all: $(PRG)
 
@@ -13,7 +14,7 @@ $(PRG): $(OBJS)
 
 %.o: ../src/%.c
 	gcc -O3 -g3 -Wall -Werror -c -std=gnu99 -MMD -MP \
-		-fno-strict-aliasing -Wno-unused \
+		-fno-strict-aliasing -Wno-unused $(DEBUG) \
 		-MF"$(@:%.o=%.d)" -MT"$(@:%.o=%.d)"\
 		-o "$@" "$<"
 

src/gdb-server.c

@@ -95,7 +95,9 @@ int serve(struct stlink* sl, int port) {
 			return 1;
 		}
 
-		//printf("recv: %s\n", packet);
+		#ifdef DEBUG
+		printf("recv: %s\n", packet);
+		#endif
 
 		char* reply = NULL;
 
@@ -246,7 +248,9 @@ int serve(struct stlink* sl, int port) {
 		}
 
 		if(reply) {
-			//printf("send: %s\n", reply);
+			#ifdef DEBUG
+			printf("send: %s\n", reply);
+			#endif
 
 			int result = gdb_send_packet(client, reply);
 			if(result != 0) {