[gdb] Do not set `disassembly-flavor` on non-x86 platforms.

The `set disassembly-flavor` command is only available when debugging a x86
target. On other targets, sourcing `tools/gdbinit` fails as a result.

Sadly, we have to resort to using python's exception to ignore errors and carry
on.

NOTRY=true

Change-Id: If37450ee5bca43d5edb02fa9a5b218d7992f8885
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1847353
Commit-Queue: Pierre Langlois <pierre.langlois@arm.com>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64182}

tools/gdbinit

@@ -138,7 +138,13 @@ Find the location of a given address in V8 pages.
 Usage: heap_find address
 end
 
-set disassembly-flavor intel
+# The 'disassembly-flavor' command is only available on i386 and x84_64.
+python
+try:
+  gdb.execute("set disassembly-flavor intel")
+except gdb.error:
+  pass
+end
 set disable-randomization off
 
 # Install a handler whenever the debugger stops due to a signal. It walks up the