[pdb] Fix libc++ strict-weak-ordering assertion failures from gsiRecordCmp (#183749)

Builds using libc++ hardening was hitting asserts like

  libc++ Hardening assertion
  !__comp(*(__first + __a), *(__first + __b)) failed:
  Your comparator is not a valid strict-weak ordering

printf-debugging revealed that symbols like "?ST@@3JA" were not
comparing equal with themselves. It turns out the comparison was done
with

  return S1.compare_insensitive(S2.data());

and even when &S1 == &S2, S1 and S2.data() may not refer to identical
strings, since data() may not have a null terminator where the StringRef
locally ends.

This fixes the ordering, simplifies the code, and makes it a little
faster :)

Fixes: #163755
1 file changed
tree: 588d5158af4472745256584198451db8e15e80cb
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. flang-rt/
  11. libc/
  12. libclc/
  13. libcxx/
  14. libcxxabi/
  15. libsycl/
  16. libunwind/
  17. lld/
  18. lldb/
  19. llvm/
  20. llvm-libgcc/
  21. mlir/
  22. offload/
  23. openmp/
  24. orc-rt/
  25. polly/
  26. runtimes/
  27. third-party/
  28. utils/
  29. .clang-format
  30. .clang-format-ignore
  31. .clang-tidy
  32. .git-blame-ignore-revs
  33. .gitattributes
  34. .gitignore
  35. .mailmap
  36. CODE_OF_CONDUCT.md
  37. CONTRIBUTING.md
  38. LICENSE.TXT
  39. pyproject.toml
  40. README.md
  41. SECURITY.md
README.md

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