ld: can't open output file for writing: a.out, errno=13 for architecture x86_64

While compiling a simple C programme, just to test the gcc compiler that comes with Xcode 4.1, I encountered the following error.

ld: can't open output file for writing: a.out, errno=13 for architecture x86_64

This got resolved by doing the following.

sudo bash

export ARCHFLAGS='-arch i386 -arch x86_64'

Then recompiling the code from within bash.

It appears that Xcode 4.x does no longer support non x86_64 architectures by default. Can somebody clearly explain this problem?