[llvm] [Offload]: Skip copying of unused kernel-mapped data (PR #124723)

[Jan Patrick Lehr via llvm-commits]

jplehr wrote:

I checked out the PR and used the CMake cache file from `offload/cmake/caches/AMDGPUBot.cmake` for my build config. I get a build error. It seems this was accidentally rebased onto something broken.
```
[1105/7623] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/CFIFixup.cpp.o
FAILED: lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/CFIFixup.cpp.o
```

I rebased onto current `main` which let me build and run tests. Failures that appears previously appear to be addressed.

https://github.com/llvm/llvm-project/pull/124723