[llvm] [MC,COFF] .safeseh: avoid changeSection (PR #132624)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> `.safeseh` is not invented by LLVM; it's invented by Microsoft: https://learn.microsoft.com/en-us/cpp/assembler/masm/dot-safeseh?view=msvc-170
> 
> It creates some metadata (indexes of symbols to safe exception handlers) in the `.sxdata` section.

The point was not that LLVM has invented what the `.safeseh` directive produces - however Microsoft don't use GAS style assembly and don't relate to such directives. In that realm, GAS/binutils is the reference, defining the semantics of the directives. But as binutils doesn't support any `.safeseh` directive, it is an LLVM invented GAS directive.

https://github.com/llvm/llvm-project/pull/132624