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

[Rainer Orth via llvm-commits]

rorth wrote:

> Taking out the WIP status since I think this is ready for merging now. (Aside from the one asan failure case - but if GCC also fails there that means that at least we're on par with it, no?)

I've just retried the testcase on Linux/i386 with `gcc-14`, where it `FAIL`s as well.  It may well depend on `-mllvm -asan-instrument-dynamic-allocas` which `gcc` obviously doesn't support.

That said, I'm fine with merging the patch now, with one caveat: please first file an Issue for the remaining failure with everything that's known about the issue, then `XFAIL` the testcase on SPARC to avoid the Solaris/sparcv9 bot turning red immediately (oh wait, it already is due to PR #106951 ;-().

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