Blender Git Loki

Clang/GCC: use relative path in __FILE__ macro

This change removes the user-specific information from
macros like `__FILE__` and keeps it relative to top level
source or build (for generated files) directory.
It makes traces concise.

Added option `WITH_COMPILER_SHORT_FILE_MACRO` enabled by default.

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D9386