[llvm] [llvm-objcopy] Don't remove .gnu_debuglink section when using --strip-all (PR #78919)

[Felix Kellenbenz via llvm-commits]

felixkellenbenz wrote:

Thanks @jh7370  for merging the PR, also thanks @MaskRay for running the checks.

Since the checks that @MaskRay performed passed,  and the I could not find something in the test failures of the build bots related to my changes, I will contact the person who raised the issue and ask them to close it.

https://github.com/llvm/llvm-project/pull/78919