[llvm] [WIP][SPARC] Allow overaligned `alloca`s (PR #107223)

[via llvm-commits]

koachan wrote:

> Just for reference, I've posted the patches I've used for my ASan testing: PR #107403 for the driver side and PR #107405 for enabling the ASan tests in `compiler-rt`.

Are these patches for Solaris only or do they apply for Linux too?
I'd like to try the asan tests too, but after applying them on my Linux box it seems like `check-asan` is still not available:
```
$ ninja check-asan
ninja: error: unknown target 'check-asan', did you mean 'check-all'?
```

https://github.com/llvm/llvm-project/pull/107223