[clang] [clang] Enable descriptions for --print-supported-extensions (PR #66715)

[David Spickett via cfe-commits]

DavidSpickett wrote:

Looks good to me, thanks for working on this.

I'm not sure if you'll have permissions to click the merge button but if you do, go ahead. Please remember to edit the final commit message to remove the links to the output files.

https://github.com/llvm/llvm-project/pull/66715