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

[Balint Cristian via cfe-commits]

cbalint13 wrote:

@DavidSpickett ,

Addressed all requests.
* Here is the console output: [console-output.txt.gz](https://github.com/llvm/llvm-project/files/12677908/console-output.txt.gz)
```
$ zcat ~/console-output.txt.gz | grep 'print'
$ ./bin/clang --target=arm-unknown-linux-gnu --print-supported-extensions
$ ./bin/clang --target=aarch64-unknown-linux-gnu --print-supported-extensions
$ ./bin/clang --target=riscv64-unknown-linux-gnu --print-supported-extensions
```

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