Re: tweak for documentation of how to create universal binaries

[Bruno Haible]

Ralf Wildenhues wrote:
> depend.m4 could detect universal builds, and in
> that case discard any problematic dependency extractors.  That means, in
> effect that only "slow" extraction mechanisms are eligible (and will
> thus be chosen only if --enable-dependency-tracking was passed
> explicitly).

This would be desirable, yes.

> The patch below (against Automake) should do the trick.
> Can you try it out, and report back the depmode chosen with and without
> --enable-dependency-tracking and whether the depmode works (in case of
> doubt, you can run depcomp7.test from the Automake testsuite)?

Without option --enable-dependency-tracking:
The depmode is now 'none' (was 'gcc' earlier). "make" and "make check" work
fine.

With option --enable-dependency-tracking:
The depmode is now 'makedepend'. There are some warnings from makedepend:
makedepend: warning:  cannot open "i386"
makedepend: warning:  cannot open "x86_64"
makedepend: warning:  cannot open "ppc"
makedepend: warning:  cannot open "ppc64"
But nothing fatal. It works.

> Can you also try to see if the "icc" depmode bit can be omitted from the
> patch?

At this point in time, "icc" for MacOS X does not support the "-arch"
option that Apple's gcc supports. The icc documentation [1] states that in order
to create universal binaries on MacOS X, one should call icc twice and combine
the resulting object files using the 'lipo' tool.

Bruno

[1] 
http://software.intel.com/en-us/articles/intel-c-compiler-professional-edition-for-mac-os-x-documentation/