This changes make_lexer() so that it no longer generates a custom target
but instead attaches the generated files to an existing one (so the first
argument now is the name of an existing library or executable, and it needs
to come after the add_library/add_executable call).
The generated source is no longer listed in the project sources, as it is
added by the function. The files are generated in the build tree rather
than the source tree, and the directory is added to the include path for
the respective project as well as exported to projects linking against it.
Generated files in subdirectories are somewhat supported, but need to be
referenced with the same name as they were generated (i.e. including the
subdirectory name).
Fixes: lp:1831643
* https://bugs.launchpad.net/kicad/+bug/1831643
Fixes: lp:1832357
* https://bugs.launchpad.net/kicad/+bug/1832357
Fixes: lp:1833851
* https://bugs.launchpad.net/kicad/+bug/1833851
c8c3e1f96a