We need to deal with the fact that in the debug info, the base directory used to interpret relative directories will be the output directory, rather than the current directory at the time of compilation.
BIR locations are used both for debug information and for error messages (in verify). The base directory for each use case is different.
We also don't want absolutize directories in LL files, because we are checking in LL files.
But with #812, BIR verification may be optional, which makes dual use less of an issue. (If you want to verify the BIR, we could generate it with source directory not output.)
We need to deal with the fact that in the debug info, the base directory used to interpret relative directories will be the output directory, rather than the current directory at the time of compilation.
BIR locations are used both for debug information and for error messages (in verify). The base directory for each use case is different.
We also don't want absolutize directories in LL files, because we are checking in LL files.