[clang] [llvm] [AArch64][RISCV] Improve the tests for --print-enabled-extensions and --print-supported-extensions (PR #97829)

[Tomas Matheson via llvm-commits]

tmatheson-arm wrote:

> Mind sticking it in a gist at least so folks can use it for downstream subtargets?

[Here you go](https://gist.github.com/tmatheson-arm/333dd14cc1c95ab4ac563ed615add95d)

https://github.com/llvm/llvm-project/pull/97829