[clang-tidy] Don't issue cppcoreguidelines-macro-usage on builtin macros

Before the patch calling clang-tidy with -header-filter=.* -system-headers would
result in a few hundred useless warnings:
  warning: macro '_GNU_SOURCE' used to declare a constant; consider using a 'constexpr' constant [cppcoreguidelines-macro-usage]
  warning: macro '_LP64' used to declare a constant; consider using a 'constexpr' constant [cppcoreguidelines-macro-usage]
  warning: macro '__ATOMIC_ACQUIRE' used to declare a constant; consider using a 'constexpr' constant [cppcoreguidelines-macro-usage]
  warning: macro '__ATOMIC_ACQ_REL' used to declare a constant; consider using a 'constexpr' constant [cppcoreguidelines-macro-usage]
  warning: macro '__ATOMIC_CONSUME' used to declare a constant; consider using a 'constexpr' constant [cppcoreguidelines-macro-usage]
  warning: macro '__ATOMIC_RELAXED' used to declare a constant; consider using a 'constexpr' constant [cppcoreguidelines-macro-usage]
  warning: macro '__ATOMIC_RELEASE' used to declare a constant; consider using a 'constexpr' constant [cppcoreguidelines-macro-usage]
  warning: macro '__ATOMIC_SEQ_CST' used to declare a constant; consider using a 'constexpr' constant [cppcoreguidelines-macro-usage]
  warning: macro '__BIGGEST_ALIGNMENT__' used to declare a constant; consider using a 'constexpr' constant [cppcoreguidelines-macro-usage]
  ... and so on

llvm-svn: 358621
2 files changed
tree: eb34e3426fd51b3118d83a43a0e915742ccc8499
  1. clang/
  2. clang-tools-extra/
  3. compiler-rt/
  4. debuginfo-tests/
  5. libclc/
  6. libcxx/
  7. libcxxabi/
  8. libunwind/
  9. lld/
  10. lldb/
  11. llgo/
  12. llvm/
  13. openmp/
  14. parallel-libs/
  15. polly/
  16. pstl/
  17. .arcconfig
  18. .clang-format
  19. .clang-tidy
  20. .gitignore
  21. README.md
README.md

The LLVM Compiler Infrastructure

This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments.