[scudo] Do not include sanitizer_posix.h if not on a Posix platform

[cryptoad]

Summary

Move the sanitizer_posix.h include within the SANITIZER_ANDROID #if,
otherwise this errors when built on non-Posix platforms (eg: Fuchsia).

lib/scudo/scudo_utils.cpp

 //===-- scudo_utils.cpp -----------------------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// Platform specific utility functions.
 ///
 //===----------------------------------------------------------------------===//
 
 #include "scudo_utils.h"
 
-#include "sanitizer_common/sanitizer_posix.h"
-
 #include <stdarg.h>
 #if defined(__x86_64__) || defined(__i386__)
 # include <cpuid.h>
 #endif
 #if defined(__arm__) || defined(__aarch64__)
 # if SANITIZER_ANDROID && __ANDROID_API__ < 18
 // getauxval() was introduced with API level 18 on Android. Emulate it using
 // /proc/self/auxv for lower API levels.
+#  include "sanitizer_common/sanitizer_posix.h"
+
 #  include <fcntl.h>
 
 #  define AT_HWCAP 16
 
 namespace __sanitizer {
 
 uptr getauxval(uptr Type) {
   uptr F = internal_open("/proc/self/auxv", O_RDONLY);