cad/calculix: Split the ccx analyzer out of the main port.
CalculiX has alwasy been comoposed of two independent packages: ccx and
cgx. Ccx, the main tool for doing FEA, depends on fortran and currently
has to be built with GCC. Cgx, on the other hand, uses OpenGL and the C++
libraries it depends on are built with our native clang so buuilding it
with GCC causes C++ library conflicts.
By making ccx an independent port we can better focus on the specific
requirements of each tool and avoid compiler-related conflicts. This also
helps the port work again with newer versions GCC.
PR: 219290. 22043, 220434
Approved by: gerald