How to link an arm .o file into an Xcode project

Question

I have a gnu built object file I need to include in an Xcode iPhone project. The .o file format is arm, via 'otool -h':

Mach header magic cputype cpusubtype caps filetype ncmds sizeofcmds flags 0xfeedface 12 0 0x00 1 3 1316 0x00002000

But Xcode rejects it, complaining that "file is not of required architecture". It accepts arm6 files (e.g. cpusubtype=6) but I am struggling to modify the GNU makefile to produce arm6 libraries.

Is there an Xcode project setting that allows linking in arm object files?

Environment:
Xcode: 3.1.4
iPhone SDK: 2.2.1
Arch: Standard (armv6)