Rollup merge of #139261 - RalfJung:msvc-align-mitigation, r=oli-obk

mitigate MSVC alignment issue on x86-32

This implements mitigation for rust-lang/rust#112480 by stopping to emit `align` attributes on loads and function arguments when building for a win32 MSVC target. MSVC is known to not properly align `u64` and similar types, and claiming to LLVM that everything is properly aligned increases the chance that this will cause problems.

Of course, the misalignment is still a bug, but we can't fix that bug, only MSVC can.

Also add an errata note to the platform support page warning users about this known problem.

try-job: `i686-msvc*`

Author: matthiaskrgr