Adjust libsanitizer to ABI change in glibc 2.31.

Taken from this upstream commit:
https://github.com/llvm/llvm-project/commit/947f9692440836dcb8d88b74b69dd379d85974ce

diff --git a/lib/sanitizer_common/sanitizer_platform_limits_posix.cc b/lib/sanitizer_common/sanitizer_platform_limits_posix.cc
--- a/lib/sanitizer_common/sanitizer_platform_limits_posix.cc
+++ b/lib/sanitizer_common/sanitizer_platform_limits_posix.cc
@@ -1126,8 +1126,9 @@ CHECK_SIZE_AND_OFFSET(ipc_perm, uid);
 CHECK_SIZE_AND_OFFSET(ipc_perm, gid);
 CHECK_SIZE_AND_OFFSET(ipc_perm, cuid);
 CHECK_SIZE_AND_OFFSET(ipc_perm, cgid);
-#if !defined(__aarch64__) || !SANITIZER_LINUX || __GLIBC_PREREQ (2, 21)
-/* On aarch64 glibc 2.20 and earlier provided incorrect mode field.  */
+#if !SANITIZER_LINUX || __GLIBC_PREREQ (2, 31)
+/* glibc 2.30 and earlier provided 16-bit mode field instead of 32-bit
+   on many architectures.  */
 CHECK_SIZE_AND_OFFSET(ipc_perm, mode);
 #endif
 
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h b/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h
--- a/lib/sanitizer_common/sanitizer_platform_limits_posix.h
+++ b/lib/sanitizer_common/sanitizer_platform_limits_posix.h
@@ -203,28 +203,15 @@ namespace __sanitizer {
     u64 __unused1;
     u64 __unused2;
 #elif defined(__sparc__)
-#if defined(__arch64__)
-    unsigned mode;
-    unsigned short __pad1;
-#else
-    unsigned short __pad1;
-    unsigned short mode;
-    unsigned short __pad2;
-#endif
-    unsigned short __seq;
-    unsigned long long __unused1;
-    unsigned long long __unused2;
-#elif defined(__mips__) || defined(__aarch64__) || defined(__s390x__)
-    unsigned int mode;
-    unsigned short __seq;
-    unsigned short __pad1;
-    unsigned long __unused1;
-    unsigned long __unused2;
+  unsigned mode;
+  unsigned short __pad2;
+  unsigned short __seq;
+  unsigned long long __unused1;
+  unsigned long long __unused2;
 #else
-    unsigned short mode;
-    unsigned short __pad1;
-    unsigned short __seq;
-    unsigned short __pad2;
+  unsigned int mode;
+  unsigned short __seq;
+  unsigned short __pad2;
 #if defined(__x86_64__) && !defined(_LP64)
     u64 __unused1;
     u64 __unused2;
535605b35e'>guix-daemon.sh</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/guix-daemon.sh?id=23aa12fc092c69228c6a636897f17c535605b35e&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-04-19 19:06:26 +0200'>2018-04-19</span></td><td><a href='/guix/commit/tests/guix-daemon.sh?id=5cefb13ddd4d51a63a387e74c138035b7b8b8537'>guix-daemon: Disable garbage collection for remote connections.</a><span class='msg-avail'>...</span></td><td>Roel Janssen</td></tr>
<tr><td><span title='2018-01-07 23:47:22 +0100'>2018-01-07</span></td><td><a href='/guix/commit/tests/guix-daemon.sh?id=29a686688674dc875775305312513405fa396a06'>daemon: Add gzip log compression.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-06-22 10:59:07 +0200'>2017-06-22</span></td><td><a href='/guix/commit/tests/guix-daemon.sh?id=1071f781d97509347144754b3248581cf7c6c1d5'>daemon: '--listen' can be passed several times, can specify TCP endpoints.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-06-04 00:35:55 +0200'>2017-06-04</span></td><td><a href='/guix/commit/tests/guix-daemon.sh?id=2ca9f51ec8125c0124362300853365a1a6c76ee5'>daemon: Add '--timeout' and '--max-silent-time'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>