gcc: fix libsanitizer build with _FILE_OFFSET_BITS=64

After the commit f67a4f50e2ace3a2 "gcc: preserve CXXFLAGS_FOR_TARGET"
target CFLAGS are passed to all libraries bundled with gcc. This breaks
libsanitizer on gcc-4.9.x when building with _FILE_OFFSET_BITS=64:

  error: size of array ‘assertion_failed__837’ is negative
  ...
  libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc:837:1:
  note: in expansion of macro ‘CHECK_SIZE_AND_OFFSET’
  CHECK_SIZE_AND_OFFSET(dirent, d_ino);

This issue is fixed in the libsanitizer mainline and in gcc-5.x.
There's no issue with gcc-4.8.x and earlier.

Reported-by: Julien CORJON <corjon.j@ecagroup.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Backported from: https://llvm.org/svn/llvm-project/compiler-rt/trunk@220328
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/gcc/4.9.3/140-sanitizer-Fix-build-with-_FILE_OFFSET_BITS-64.patch

@@ -0,0 +1,37 @@
+From 3c536954a67a883630f4a7513a27f02a892c3dcb Mon Sep 17 00:00:00 2001
+From: Evgeniy Stepanov <eugeni.stepanov@gmail.com>
+Date: Tue, 21 Oct 2014 21:08:13 +0000
+Subject: [PATCH] [sanitizer] Fix build with _FILE_OFFSET_BITS=64.
+
+Sanitizer source is not affected by _FILE_OFFSET_BITS in general,
+but this one file must be built with 32-bit off_t. More details in the code.
+
+git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@220328 91177308-0d34-0410-b5e6-96231b3b80d8
+Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
+---
+ lib/sanitizer_common/sanitizer_platform_limits_posix.cc | 8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+diff --git a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc
+index bbc1108..fc09522 100644
+--- a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc
++++ b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc
+@@ -13,7 +13,15 @@
+ 
+ #include "sanitizer_platform.h"
+ #if SANITIZER_LINUX || SANITIZER_MAC
++// Tests in this file assume that off_t-dependent data structures match the
++// libc ABI. For example, struct dirent here is what readdir() function (as
++// exported from libc) returns, and not the user-facing "dirent", which
++// depends on _FILE_OFFSET_BITS setting.
++// To get this "true" dirent definition, we undefine _FILE_OFFSET_BITS below.
++#ifdef _FILE_OFFSET_BITS
++#undef _FILE_OFFSET_BITS
++#endif
+ 
+ #include "sanitizer_internal_defs.h"
+ #include "sanitizer_platform_limits_posix.h"
+ 
+-- 
+2.1.4
+