How is that different from standard automake stuff?
I do not know where USE_ASPELL etc come from, and what exactly it is. I actually need to look up other .m4 files (or google) to know how to write a if/else block. (I know, that is only me.)
I can see how this can get us autoconf+scons. But I guess this is not a big gain. The bigger part is actually doing the autoconf part.
The saving of compiling time is a big gain for us. The autoconf capacity of scons is OK, and is easier to use. Bo