[sandbox] Temporarily disable sandboxed pointers on ChromeOS

They are causing failures in the Linux ChromiumOS MSan bot.

Bug: chromium:1324301
Change-Id: I7a7bcd111a9f0e0e652d38e107027c51e51bd4bc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3639205Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Auto-Submit: Samuel Groß <saelo@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80463}

BUILD.gn

@@ -508,7 +508,8 @@ if (v8_enable_sandbox) {
   # sandbox. As such, disable the sandbox there. See https://crbug.com/1323174
   if (!is_asan && !is_hwasan && !is_lsan && !is_tsan && !is_msan) {
     v8_enable_sandboxed_pointers =
-        target_os != "fuchsia" && target_os != "android"
+        target_os != "fuchsia" && target_os != "android" &&
+        target_os != "chromeos"
   }
 }