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

[Paschalis Mpeis via llvm-commits]

================
@@ -49,6 +49,11 @@ static cl::opt<bool>
                      cl::desc("aggregate basic samples (without LBR info)"),
                      cl::cat(AggregatorCategory));
 
+cl::opt<bool> ArmSPE("spe",
+                     cl::desc("Enable Arm SPE mode. Can combine with `--nl` "
+                              "to use in no-lbr mode"),
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paschalis-mpeis wrote:

```suggestion
                     cl::desc("Enable Arm SPE mode."),
```

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