Fix build error under OS X.

Makefile

  -Wshadow -Wformat-security -Wstrict-prototypes -Wno-unused-parameter \
  -Wredundant-decls -Wold-style-definition
 
+uname_S := $(shell sh -c 'uname -s 2>/dev/null || echo not')
+
 LDFLAGS ?= -Wl,--gc-sections
 
+ifeq ($(uname_S),Darwin)
+LDFLAGS :=
+endif
+
 DEFS += -D_FILE_OFFSET_BITS=64
 
 FUNCS_DIR = libfuncs

util.c

 #include <stdlib.h>
 #include <string.h>
 #include <inttypes.h>
-#include <malloc.h>
 #include <unistd.h>
 
 #include "util.h"
 }
 
 void *xmalloc(size_t size) {
-	void *ret = memalign(16, size);
+	void *ret = malloc(size);
 	if (!ret)
 		die("Can't alloc %ld bytes\n", (unsigned long)size);
 	return ret;