file was built for i386 which is not the architecture being linked (x86_64) while compiling OpenCV2.2 for iOS 4.2 on Mac OSX 10.6

Question

I have been following the simple guide at http://www.atinfinity.info/wiki/index.php?OpenCV/Using%20OpenCV%202.2%20on%20iOS%20SDK%204.2 (which uses the older guide I've also read at http://niw.at/articles/2009/03/14/using-opencv-on-iphone/en) to get OpenCV2.2 compiled to work on iOS 4.2. Everything went smoothly until I tried to build. When I run the following:

lc:opencv_simulator leonard$ ../opencv_cmake.sh Simulator ../../OpenCV-2.2.0/

I get the following error:

ld: warning: in /Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.2.sdk/usr/lib/libSystem.dylib,
  file was built for i386 which is not the architecture being linked (x86_64)

This is using (among other settings, obviously):

-D CMAKE_OSX_ARCHITECTURES="i386"

I read that on OSX 10.6 i386 is seen as the default, so it uses the system default (but that is x86_64). I also read I could use:

export CFLAGS=-m32
export CPPFLAGS=-m32

But this doesn't work either.

Any ideas?

Solution

The gcc flag for building a specific architecture is -march as in

gcc -march=i386 ...