[clang] [llvm] Add support in LLVM BitstreamWriter to automatically choose abbrevs. (PR #147191)

[Chuanqi Xu via llvm-commits]

https://github.com/ChuanqiXu9 commented:

This looks much better but we still have to record the layout twice. Once in Visit* methods and once in ASTWriterDecl. I fear the records in ASTWriterDecl get outdated quickly.

https://github.com/llvm/llvm-project/pull/147191