Is glib-2 available on our iDevices? And do we have an i368 or amd64 system?
iOS is little-endian arm6 or arm7 (if you specify arm it'll be OK) with mach-o executables. If there's nothing specifically for iOS you should choose 32bit options with configure. (I did this for openssl)
Most libs aren't symlinked properly by installsdk3 so search for them under /private/var/sdK/usr/lib/libname.dylib and eventually symlink them to /usr/local/lib.
crt_externs.h has never been part of the iOS SDK but you can get a copy from the iPhoneSimulator SDK