Jan Schaumann suggested following idea.

Jan Schaumann wrote:
> Hi,
> 
> Some time ago, you switched firefox to use gtk2.  Not every user may
> want that, though.  Instead of hardcoding the MOZILLA_USE_GTK2 variable
> into the makefile, could you turn it into a knob that can be set by the
> user?
> 
> Thanks,
> -Jan
> 

It's not so difficult to do this.
But I worry about following issues.

(1)Is it OK for pkgsrc to have configure options that makes huge difference?
I known about PKG_OPTIONS and many packages are configurable.
But they does not make large difference.

(2)Is this OK for the packages that depends firefox?
It is sometime gtk1 based, sometime gkt2 based, depends on the variable.
It would be the problem expecially for binary packages.

Any comments?