Move generic start code and memset into arch/generic.h

arch/aarch64.c

@@ -1,6 +1,8 @@
 #if defined(__aarch64__)
 #include "../int.h"
 
+#include "generic.h"
+
 void exit(int8_t status){
   asm ( "mov x0, %0\n"        // Move the exit status into register x0
         "mov x8, #93\n"       // Syscall number for 'exit' is 93 in AArch64