title: Clang-Tidy llvm-header-guard directory configuration
body: <p>Is there a way to remove the suggested computer specific path on the suggested llvm-header-guard string when running static analysis with clang-tidy?</p>
  
  <p>For example the suggested header guard for the file (cls/math/matrix.hpp) is:
      _USERS_NAME_DESKTOP_PROJECT_SRC_CLS_MATH_MATRIX_HPP</p>
  
  <p>But to avoid making this specific to my computer it should only be:
      _PROJECT_SRC_CLS_MATH_MATRIX_HPP</p>
  
  <p>Is there a way to configure clang-tidy such that it suggests header guards starting from the /project/ directory rather than the /users/ directory?</p>
  
  <p>I am using clang 5.0.0, running from cmake.</p>