I noticed a case where Torque can generate an invalid .inc file, and I
think that it's worth adding a check that can emit an error during
run_torque rather than letting the developer hit a C++ compilation
failure later.

Example error message, if you add @export to StrongDescriptorArray:

Torque Error: Exported class StrongDescriptorArray cannot be in the same
              file as its parent extern class DescriptorArray

Bug: v8:7793
Change-Id: Ia69124a4177bd7a53f95442249fae88cb16e354a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3015655Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#75662}