Standardize NO_CCACHE flag and ccache definitions

[Alex Dupre]

Edwin Groothuis ha scritto:
> Recently I've started to use devel/ccache again (sometimes it takes
> a while before you understand how it works) and it works pretty
> well, except for some ports which can't be build with it. For example
> devel/cmake.

I use ccache everywhere (world and ports) and I never found a port that 
doesn't compile with it (I have cmake, too).

-- 
Alex Dupre