[AST][NFC] Remove temporary ASTTU file from Introspection generation.

We can use the Preprocessor to remap this file, cleaning up the cmake code.

Reviewed By: steveire

Differential Revision: https://reviews.llvm.org/D100343

GitOrigin-RevId: bfb6c2874be830cc6f7595652d23192598edecf0
2 files changed