[grokdump] Fix outdated arm64 identifier value

Breakpad used to put a custom identifier 0x8003 into minidumps to
indicate arm64 architecture. Crashpad now uses the new standardized
value 12. This CL updates grokdump.py to understand both.

Change-Id: Ie9bf5106beba8059e89a48d42d32ac8069493925
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1648258
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62047}

tools/grokdump.py

@@ -586,7 +586,10 @@ MINIDUMP_RAW_SYSTEM_INFO = Descriptor([
 
 MD_CPU_ARCHITECTURE_X86 = 0
 MD_CPU_ARCHITECTURE_ARM = 5
-MD_CPU_ARCHITECTURE_ARM64 = 0x8003
+# Breakpad used a custom value of 0x8003 here; Crashpad uses the new
+# standardized value 12.
+MD_CPU_ARCHITECTURE_ARM64 = 12
+MD_CPU_ARCHITECTURE_ARM64_BREAKPAD_LEGACY = 0x8003
 MD_CPU_ARCHITECTURE_AMD64 = 9
 
 OBJDUMP_BIN = None
@@ -647,6 +650,8 @@ class MinidumpReader(object):
         system_info = MINIDUMP_RAW_SYSTEM_INFO.Read(
             self.minidump, d.location.rva)
         self.arch = system_info.processor_architecture
+        if self.arch == MD_CPU_ARCHITECTURE_ARM64_BREAKPAD_LEGACY:
+          self.arch = MD_CPU_ARCHITECTURE_ARM64
         assert self.arch in [MD_CPU_ARCHITECTURE_AMD64,
                              MD_CPU_ARCHITECTURE_ARM,
                              MD_CPU_ARCHITECTURE_ARM64,