The library you're liking to is not of the same architecture as the library your linking (./../extern/libexif-0.6.19/libexif/.libs/libexif.a).

libexif.a is an i386 arch. Check your build settings to ensure that you're building an i386 binary or recompile the libexif.a to match your build target arch.

fyi, If you're using Xcode, then by default Debug mode only builds your platforms native arch. So on a new mac, this would be an x86_64 binary.