[llvm] [llvm-cov] Migrate gcov to OptTable (PR #224955)

[Fangrui Song via llvm-commits]

MaskRay wrote:

Context: Apple/Google contributed a lot of gcov instrumentation and llvm-cov gcov. Around 2020, I rewrote a large portion of the tool and implemented several gcov options. Backward compatibility is minimal concern (for Bazel the gcov infrastructure is still compatible with GCC), especially as many organizations have since migrated to Clang source-based code coverage.

https://github.com/llvm/llvm-project/pull/224955