Building Ruby 1.9.3 on Lion with Xcode 4.2 using ./configure --with-gcc=clang

Question

My environment: Mac OS X v10.7.2 with Xcode 4.2.1

I am trying to build ruby 1.9.3 on Lion with Xcode 4.2.1. I understand there's an issue with the llvm-based gcc compiler that comes with Xcode 4.2.1. But I'm trying to work around it by following these instructions, http://goo.gl/Sc39g. I was able to get a little farther along, but then ran into these 2 problems:

1. #error Please add -D_FILE_OFFSET_BITS=64 to your compile flags!
2. fatal error: 'sys/statfs.h' file not found

The complete configure output is here: http://cl.ly/2q2G3p3r3S133i0U1i1e (the errors are all the way in the bottom)

Please advise. Thanks in advance.

P.S. I've read the list of similar/related questions, but none seem to address these 2 particular errors, or I missed them as my eyes are starting to glaze over from all the things I've tried to get this build to work. If this question has already been answered, please point me to the answer, and accept my apologies for the duplication.