lldb/test/Shell/Watchpoint/LocalVariableWatchpointDisabler.test is not run anywhere

Found while investigating https://github.com/llvm/llvm-project/issues/217961.

A suspect patch for that issue is https://github.com/llvm/llvm-project/commit/0dd62ace2ee2fafcb9a08953db1b9e4e20428e28, which added this test case as Darwin only. I don't immediately see a technical reason for that, maybe just caution.

Then @jasonmolenda disabled the test on Darwin "temporarily" :) So we now have:
```
# REQUIRES: system-darwin
<...>
# UNSUPPORTED: system-darwin
```
* It would be good to get this running on Darwin again, and -
* Running anywhere, as there's a chance it would have detected https://github.com/llvm/llvm-project/issues/217961 earlier (albeit accidentally).

Start with lldb/test/Shell/Watchpoint/LocalVariableWatchpointDisabler.test and inspect its REQUIRES and UNSUPPORTED directives, along with the linked issue 217961 and the referenced commit. Run the test through the LLDB shell test suite on Darwin and another supported system; done means it is no longer excluded and executes successfully where appropriate.

Written by the indexing model from the issue text.