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

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

One more minor round of comments. Please note that I am not going to be in much of next week and will likely not have time to review further. I am happy for @mstorsjo to approve in my absence once my comments have been addressed.

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