[llvm] [PGO] Ensure non-zero entry-count after `populateCounters` (PR #112029)

[Ellis Hoag via llvm-commits]

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+; RUN: llvm-profdata merge %S/Inputs/fix_entry_count_sampled.proftext -o %t.profdata
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ellishg wrote:

Since this input `.proftext` file is only used for this test, can we use `split-file` and inline it here?

https://llvm.org/docs/TestingGuide.html#extra-files

https://github.com/llvm/llvm-project/pull/112029