[llvm] [llvm-profdata] Enabled functionality to write split-layout profile (PR #101795)

[Lei Wang via llvm-commits]

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+RUN: llvm-profdata merge --sample --extbinary --split_layout %p/Inputs/sample-profile.proftext -o %t-output
+RUN: diff %t-output %p/Inputs/split-layout.profdata
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wlei-llvm wrote:

> Note that there is no way to represent flat profile in text mode, I will have to implement that

Maybe we can try `--show-sec-info-only` to check the section size. The size would change if others remove what you adds. 

https://github.com/llvm/llvm-project/pull/101795