In order to support hot-patching, we need to make sure the first emitted instruction in a function a two-byte+ op. This is already the case on x86_64, which always emits two-byte+ ops. However on 32-bit targets this wasn't the case.
Whenever using the "patchable-function" attribute, a PATCHABLE_OP now lowers to a `xchg ax, ax`, like MSVC does.
The goal of this patch, along with D43002 and D81296, is to support the clang-cl flag /HOTPATCH: https://docs.microsoft.com/sv-se/cpp/build/reference/hotpatch-create-hotpatchable-image?view=vs-2019