Backport macOS ARM64 ASAN dynamic shadow offset from LLVM 12+

LLVM 10's AddressSanitizer pass uses the Linux ARM64 static shadow
offset (0x1000000000) for ALL ARM64 targets, including macOS ARM64.
However, macOS ARM64 requires a dynamic shadow offset because the ASAN
runtime maps shadow memory at a different address (0x7000020000).

This mismatch causes JIT-compiled shader code to compute wrong shadow
addresses, hitting protected memory and crashing with SIGBUS
(KERN_PROTECTION_FAILURE).

Backport the fix from LLVM 12+ which adds an IsMacOS && IsAArch64 check
to use kDynamicShadowSentinel (dynamic shadow offset) on macOS ARM64,
matching what the ASAN runtime expects.

LLVM change:
https://github.com/llvm/llvm-project/commit/176a6e7abe33d58a65ce9cfac15fe320962e7b6e

Bug: 493957482
Change-Id: I4d48bc41f89728d508d1937a1d767ea5a1576e6b
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/77208
Reviewed-by: Shahbaz Youssefi <syoussefi@google.com>
Reviewed-by: Geoff Lang <geofflang@google.com>
Commit-Queue: Shahbaz Youssefi <syoussefi@google.com>
Tested-by: Shahbaz Youssefi <syoussefi@google.com>

third_party/llvm-10.0/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

diff --git a/third_party/llvm-10.0/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/third_party/llvm-10.0/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index 79c1194..8199d5d 100644
--- a/third_party/llvm-10.0/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/third_party/llvm-10.0/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -427,6 +427,7 @@
                                       bool IsKasan) {
   bool IsAndroid = TargetTriple.isAndroid();
   bool IsIOS = TargetTriple.isiOS() || TargetTriple.isWatchOS();
+  bool IsMacOS = TargetTriple.isMacOSX();
   bool IsFreeBSD = TargetTriple.isOSFreeBSD();
   bool IsNetBSD = TargetTriple.isOSNetBSD();
   bool IsPS4CPU = TargetTriple.isPS4CPU();
@@ -503,6 +504,8 @@
       Mapping.Offset = kMIPS64_ShadowOffset64;
     else if (IsIOS)
       Mapping.Offset = kDynamicShadowSentinel;
+    else if (IsMacOS && IsAArch64)
+      Mapping.Offset = kDynamicShadowSentinel;
     else if (IsAArch64)
       Mapping.Offset = kAArch64_ShadowOffset64;
     else