The "virtual" keyword has been deprecated from the board file format so
use "exclude_from_bom" as the flag for the old virtual behavior. This
is only a partial fix. Full support for the "exclude_from_bom" will be
added later for V7.
Fixes: https://gitlab.com/kicad/code/kicad/-/issues/10563
(cherry picked from commit 497061de35)