[llvm] Allow specifying libcxx builder image. (PR #110303)

[Michael Buch via llvm-commits]

Michael137 wrote:

> > Any idea why we might fail to launch the test executable in a container (inside a container)?
> 
> You need to set up the debug session with `settings set target.disable-aslr false` so that you don't have that problem with the personality syscall. This can be done here https://github.com/llvm/llvm-project/blob/main/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py#L758 so that all launch requests use the correct setting. See that there's a disableASLR setting that you can try to have a default value for.

Given we already flipped the default to `settings set target.disable-aslr false` for all non-DAP tests, could we set `disableASLR` to `False` here too?

The behaviour is a bit inconsistent at the moment. From the logs:
```
  {
    "arguments": {
      "commandEscapePrefix": null,
      "disableASLR": true,
     ....
      "initCommands": [
        ...
        "settings set target.disable-aslr false",
```

https://github.com/llvm/llvm-project/pull/110303