fix compile error on Linux

Makefile

@@ -1,6 +1,6 @@
 localversion = $(shell bash scripts/localversion.sh)
 
-cflags = -Wall -Iinclude -Iinclude/asm/gameboy -DLOCALVERSION=\"$(localversion)\" -g -std=c99
+cflags = -Wall -Iinclude -Iinclude/asm/gameboy -DLOCALVERSION=\"$(localversion)\" -g -std=c99 -D_POSIX_C_SOURCE=200112L
 
 all:
 

src/fix/main.c

@@ -9,6 +9,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sysexits.h>
+#include <unistd.h>
 
 #include "asmotor.h"