Stack misalignment while executing SSE code

Void Linux, x64 bit, latest LLVM, 32-bit executable initializing Mesa, segfaulting with:

```
#0 0xeeb9eefe in llvm::xxh3_64bits(llvm::ArrayRef) () from /usr/lib32/libLLVM.so.21.1
#1 0xeeb45426 in llvm::StringMapImpl::hash(llvm::StringRef) () from /usr/lib32/libLLVM.so.21.1
#2 0xeead3031 in ?? () from /usr/lib32/libLLVM.so.21.1
#3 0xeeac32d9 in llvm::cl::Option::addArgument() () from /usr/lib32/libLLVM.so.21.1
```

Likely due to misaligned stack (stack is aligned in the caller `llvm::StringMapImpl::hash`):

```
=> 0xeeb9eefe <_ZN4llvm11xxh3_64bitsENS_8ArrayRefIhEE+430>: movdqa XMMWORD PTR [esp+0x20],xmm0
0xeeb9ef04 <_ZN4llvm11xxh3_64bitsENS_8ArrayRefIhEE+436>: punpckldq xmm0,xmm4
0xeeb9ef08 <_ZN4llvm11xxh3_64bitsENS_8ArrayRefIhEE+440>: movdqa xmm5,xmm1
0xeeb9ef0c <_ZN4llvm11xxh3_64bitsENS_8ArrayRefIhEE+444>: punpcklqdq xmm5,xmm0

$esp = (void *) 0xffffbeb4
```

Start by reproducing the 32-bit Mesa initialization crash on Void Linux with the reported LLVM build, then inspect the call path through llvm::StringMapImpl::hash, llvm::xxh3_64bits, and llvm::cl::Option::addArgument. Confirm whether the SSE instruction is reached with a misaligned stack and document a fix that prevents the segfault.

Written by the indexing model from the issue text.