[clang] [clang] Add CLANG_ENABLE_NEW_CONST_INTERP_BY_DEFAULT cmake option (PR #199396)

[Oliver Hunt via cfe-commits]

https://github.com/ojhunt approved this pull request.

I don't see anything particularly wrong with this - I assume that this makes it easier to test across all the existing tests that aren't manually opting in to the bytecode interpreter?

https://github.com/llvm/llvm-project/pull/199396