patch 9.1.0405: tests: xxd buffer overflow fails on 32-bit

Problem:  tests: xxd buffer overflow fails on 32-bit
Solution: Skip test on 32-bit architecture

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_xxd.vim b/src/testdir/test_xxd.vim
index 642f5e7..a91a1fc 100644
--- a/src/testdir/test_xxd.vim
+++ b/src/testdir/test_xxd.vim
@@ -412,9 +412,12 @@
 endfunc
 
 
-" Try to trigger a buffer overflow (#14738)
+" This used to trigger a buffer overflow (#14738)
 func Test_xxd_buffer_overflow()
   CheckUnix
+  if system('file ' .. s:xxd_cmd) =~ '32-bit'
+    throw 'Skipped: test only works on 64-bit architecture'
+  endif
   new
   let input = repeat('A', 256)
   call writefile(['-9223372036854775808: ' . repeat("\e[1;32m41\e[0m ", 256) . ' ' . repeat("\e[1;32mA\e[0m", 256)], 'Xxdexpected', 'D')