AC_C_BIGENDIAN vs. Darwin

[Matt Watson]

(This issue caused OpenSSH to fail to configure properly on Darwin, so 
it's not just a contrived example...)

Darwin's (g)cc driver has the ability to build for multiple 
architectures simultaneously:

cc -arch i386 -arch ppc foo.c

This will invoke the compiler once for each architecture and create a 
"fat" binary with both i386 and ppc sections. It returns a single exit 
status, non-zero if either compile failed. Unfortunately, when the 
aforementioned macro is used, it causes a compile-test to be issued like 
this:

#if BYTE_ORDER == BIG_ENDIAN
        big endian
#endif

Since the i386 side fails this #if test, it causes the entire cc to 
fail, so WORDS_BIGENDIAN is not defined for either architecture.

I'm trying to figure out the best way to fix this. Is the 
autoconf/configure mechanism just not suited to handle this form of 
compilation? Should Darwin change its build system to run autoconf once 
for each architecture?

thanks,

matt.