build_module fails to propagate cppargs argument

[James R. Maddison]

In the release version (1.2) of Instant the cppargs argument is ignored when the cmake_packages argument is non-empty. This has the consequence of DOLFIN set c++ optimisation flags being ignored, which leads to a serious performance penalty.

[James R. Maddison]

My impression (from reading the code only) is that this may already be fixed in master.

[Johan Hake]

Yes this was an unfortunate regression introduced when switching to CMake as build backend and it has been fixed in master.

[Prof Garth Wells]

I've pushed a change to FFC to use cpp optimsation by default for a better use experience. It's presently in the next branch.