This enables llvm-rc to look for its resource files in various paths. Documentation says that the path must be relative or absolute to the current working directory, however that's not whole truth. The order of directory lookup is as follows:
- Directory where .rc file resides in.
- Current working directory.
- Paths provided by -I (/I) switch, in order of the arguments.
If a relative path is given, we seek for an existing file relative to any of these locations.
Thanks for Nico Weber for his original research on this topic.