[llvm] [llvm][yaml2obj] Modify section header overriding timing (PR #130942)

[Ruoyu Qiu via llvm-commits]

cabbaken wrote:

We can see the test of `tools/yaml2obj/ELF/program-header-size-offset.yaml` [failed](https://github.com/llvm/llvm-project/blob/main/llvm/test/tools/yaml2obj/ELF/program-header-size-offset.yaml#L34) because of the unmatched `FileSize` and `MemSize` of the last PorgramHeader after delaying the `overrideFields()`.

But the code here([FileSize](https://github.com/llvm/llvm-project/blob/main/llvm/lib/ObjectYAML/ELFEmitter.cpp#L1192) and [MemSize](https://github.com/llvm/llvm-project/blob/main/llvm/lib/ObjectYAML/ELFEmitter.cpp#L1206)) shows that this is a correct action. Both the last two section of the ProgramHeader is `SHT_NOBITS`, which won't occupy physical space in a file. Is this proving that the current test has a mistake?

And I also found another two failed tests

* [`tools/llvm-readobj/ELF/malformed-pt-dynamic.test`](https://github.com/llvm/llvm-project/blob/main/llvm/test/tools/llvm-readobj/ELF/malformed-pt-dynamic.test#L43): Failed because it considers the `p_offset` is determined by `sh_offset`.
* [`tools/obj2yaml/ELF/program-headers.yaml`](https://github.com/llvm/llvm-project/blob/main/llvm/test/tools/obj2yaml/ELF/program-headers.yaml#L437): Failed because of the unmatching of the overridden `sh_offset` and the corresponding `p_offset`.

https://github.com/llvm/llvm-project/pull/130942