Libpolygon can provide its own includes via target_include_dirs PUBLIC.
This means any linking targets do not need to specifiy them manually.
As common requires polygon, the polygon dep is also now no longer
required downstream of libcommon, as it's transisitvely implied
by libcommon's target_link_libraries.
This resolves a circular dependency previously detected and also
simplifies CMakeLists.
It was added when refactoring the SHAPE_POLY_SET class, ande replace any use of CPolyLine class inside Kicad code.
the CPolyLine related code is now not used.
So this test nowadays makes no longer sense.
Replaces Poly2Tri with updated code to process polygons faster and more
robustly. Notably, we can now handle overlapping holes in the polygons,
allowing us to cache the triangulation of complex boards
This target seems to only create empty makefiles, tested on linux. And I
can not find any references to it in any of the current CMakeLists. Lets
remove it.