about debugging openfoam

[houkensjtu]

openFOAM is a huge computational fluid dynamic toolkit/library which needs tons of dependencies and happily it recently became available in portage(since 2.2).
As a openFOAM user we may want to add "debug" flag when compiling all of its components since sometimes we want to know what actually happens inside its numerical calculation. In fact this feature can be easily achieved by tweaking an option called WM_COMPILE_OPTION inside a configuration file of openfoam if I compile all things up mannually.
However now the openFOAM ebuild does not provide a "debug" USE flag, thus even I may mannually tweak the option as I want and rebuild part of the components, I believe all my customization will be wiped out after a upgrade from portage.

I suppose there will be sevral ways to solve this problem:
1. Find / Make a overlay for it and add the feature I want. But since I am not a gentoo developer, it seems somehow time-consuming for me to dig in.
2. Get rid of the "portage version" of openfoam and build myself from 0. It should be OK but what a waste of effort paid by its maintainer!
3. Mask any newer version of openfoam by package.mask, it can prevent portage from upgrading it but I think eventually I will need a upgrade to grab new features provided in openfoam.

So it seems there isnt a really perfect solution, Any advices/suggestions?

THX