[llvm] Add initial support for SPE brstack format (PR #129231)

[Paschalis Mpeis via llvm-commits]

https://github.com/paschalis-mpeis commented:

Hey Adam,

Thanks for addressing the comments. A final thing would be to reintroduce the loop for checking the samples in the unit-test.

https://github.com/llvm/llvm-project/pull/129231