[llvm] [llvm-objcopy][COFF] Update WinCFGuard section contents after stripping (PR #153322)

[Evgenii Kudriashov via llvm-commits]

e-kud wrote:

Supported `.gehcont$y` change as it is similar to cfguards. I'll try to reduce tests size a little bit later.

https://github.com/llvm/llvm-project/pull/153322