If you just want single-arch binaries, then I suggest you build
Universal, ditto the built product, then use lipo to
thin it. Much faster than compiling every file four times.
Or use ditto with the -arch <arch> option. It can copy and thin in one step.
In fact, it seems like it would be simple to make targets that execute a
shell script with a single ditto command in them. E.g. the "ppc-only'
target, which depends on the Universal target, might have a line like this:
ditto -arch ppc path/to/universal-target path/to/ppc
and for an x86-only target:
ditto -arch i386 path/to/universal-target path/to/i386
The man-page for ditto has more info. Be careful with the pathnames, ditto
is NOT like 'cp' or 'mv'.
And once the single-arch builds are in their own target, then you can make
an aggregate target that builds them all.
-- GG