[llvm] [DLCov 1/5] Add CMake option to enable enhanced line number coverage tracking (PR #107278)

[J. Ryan Stinnett via llvm-commits]

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@@ -475,6 +475,17 @@ enabled sub-projects. Nearly all of these variable names begin with
 **LLVM_ENABLE_BINDINGS**:BOOL
   If disabled, do not try to build the OCaml bindings.
 
+**LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING**:STRING
+  Enhances Debugify's ability to detect line number errors by storing extra
+  information inside Instructions, removing false positives from Debugify's
+  results at the cost of performance. Allowed values are `DISABLED` (default),
+  `COVERAGE`, and `COVERAGE_AND_ORIGIN`. `COVERAGE` tracks whether and why a
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jryans wrote:

Should we give an example performance impact for the `COVERAGE` mode here? I think it would help people evaluate how they use the feature.

https://github.com/llvm/llvm-project/pull/107278