scripts: size_report: Fix reporting on Windows

Certain symbols do not contain a valid path, instead showing
`<built-in>` in the filename attribute. This leads to the resolve() call
failing on Windows, since the `<>` characters are not allowed in
filenames there. Fix this by catching the exception and skipping the
call in that case.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>