Improve BOM generation with smart check for licenses

The current process to generate the BOM file relies on determine the license of the source files reported by dwarf2sources. Unfortunately there are several trickiness with this.

First, depending on the build system used and debian rules the values reported by dwarf2source might not match the source tree. Also the license scan tool tends to used wildcards which make the search of a file with the wrong path not to fail but to report the default license.

In order to properly fix a more strict approach should be use, as a first step in that direction, improve the BOM generation by trying to guess the path_prefix to be appended to the source file as reported by dwarf2souces to match the source tree.

Additionally avoid during a recursive scan of the folder with the copyright information since it is not required and produces misleading warnings.

https://phabricator.apertis.org/T8545

Signed-off-by: Walter Lozano walter.lozano@collabora.com