If the current working directory of `clang-include-cleaner` differs from
the directory of the input files specified in the compilation database,
it doesn't adjust the input file paths properly. As a result,
`clang-include-cleaner` either writes files to the wrong directory or
fails to write files altogether.
This pull request fixes the issue by adjusting the input file paths
based on the directory specified in the compilation database. If that
directory is not writable, `clang-include-cleaner` will write the output
relative to the current working directory.
Fixes#110843.
4cda28c1ad