[clang] [llvm] [Clang] Enable lit internal shell by default (PR #158465)

[Aiden Grossman via cfe-commits]

boomanaiden154 wrote:

> Is there a doc page for this? (grepping for "lit" was not effective :D)

There's not one explicitly for the internal shell. We might want to add a section on the man page at some point, but no one has gotten around to it because the issues where things end up being different are pretty long-tail.

https://github.com/llvm/llvm-project/pull/158465